The setup is exactly the same as in [0], except for `gpg-bridge`, where normal gpg socket is used instead of the extra socket. Please see that link for the description of the setup and configs.
I am using gpg ssh agent and ssh key on Yubikey, and:
* both machines have the Yubikey auth key in `$GNUPGHOME/sshcontrol` (not necessary according to gpg documentation, but just to eliminate potential problems)
* `ssh-add -L` prints the key on both machines:
    when plugged into local it gives:
```
    > ssh-add -L
    ssh-rsa [...] cardno:<DISPSERIALNO>
    ssh-rsa [...] (none)
```
    when plugged into remote it gives:
```
    ❯ ssh-add -L
    ssh-rsa [...] cardno:<DISPSERIALNO>
    ssh-rsa [...] (none)
```
    when plugged into local, in remote ssh it gives:
```
    ❯ ssh-add -L
    ssh-rsa [...] (none)
```
Both `cardno:<DISPSERIALNO>` and `(none)` are the same identical keys. Roughly speaking, duplicated under different names(?).
Additional comment about "Session:" below. Seems like gpg agent doesn't see the card key and ssh suggests me to plug in the card, all it sees is the `(none)` key.
Any advice on this problem?
Below are the logs of gpg-agent without any additional commentary.
# Local
Prepare for session:
    > gpgconf --kill all
    > rm ~/.gnupg/*log
    > gpg-connect-agent updatestartuptty /bye
    gpg-connect-agent: no running gpg-agent - starting 'C:\Program Files (x86)\gnupg\bin\gpg-agent.exe'
    gpg-connect-agent: waiting for the agent to come up ... (5s)
    gpg-connect-agent: connection to agent established
    OK
Session:
    ❯ ssh pc
    Last login: ...
    gpg-connect-agent: no running gpg-agent - starting '/usr/bin/gpg-agent'
    gpg-connect-agent: waiting for the agent to come up ... (5s)
    gpg-connect-agent: connection to agent established
    ❯ ssh -T git@github.com
    Please insert the card with serial number:
      <DISPSERIALNO>
      OK
      Cancel
    [oc]? o
    Please insert the card with serial number:
      <DISPSERIALNO>
      OK
      Cancel
    [oc]? c
    sign_and_send_pubkey: signing failed for RSA "(none)" from agent: agent refused operation
    git@github.com: Permission denied (publickey).
    ❯
    Connection to <REMOTE_MACHINE_IP> closed.
    >
<gpg-agent.log> after session:
    2020-09-11 07:14:29 gpg-agent[7656] listening on socket 'C:\Users\avemilia\AppData\Roaming\gnupg\S.gpg-agent'
    2020-09-11 07:14:29 gpg-agent[7656] listening on socket 'C:\Users\avemilia\AppData\Roaming\gnupg\S.gpg-agent.extra'
    2020-09-11 07:14:29 gpg-agent[7656] listening on socket 'C:\Users\avemilia\AppData\Roaming\gnupg\S.gpg-agent.browser'
    2020-09-11 07:14:29 gpg-agent[7656] listening on socket 'C:\Users\avemilia\AppData\Roaming\gnupg\S.gpg-agent.ssh'
    2020-09-11 07:14:29 gpg-agent[7656] gpg-agent (GnuPG) 2.2.23 started
    2020-09-11 07:14:29 gpg-agent[7656] putty message loop thread started
    2020-09-11 07:14:29 gpg-agent[7656] DBG: chan_0x00000284 -> OK Pleased to meet you
    2020-09-11 07:14:29 gpg-agent[7656] DBG: chan_0x00000284 <- RESET
    2020-09-11 07:14:29 gpg-agent[7656] DBG: chan_0x00000284 -> OK
    2020-09-11 07:14:29 gpg-agent[7656] DBG: chan_0x00000284 <- updatestartuptty
    2020-09-11 07:14:29 gpg-agent[7656] DBG: chan_0x00000284 -> OK
    2020-09-11 07:14:29 gpg-agent[7656] DBG: chan_0x00000284 <- [eof]
    2020-09-11 07:14:36 gpg-agent[7656] DBG: ssh map file 'WSLPageantRequest'
    2020-09-11 07:14:36 gpg-agent[7656] DBG: ssh map handle 0x00000298
    2020-09-11 07:14:36 gpg-agent[7656] DBG:           my sid: 'S-1-5-21-2866614668-1482101499-365976279-1001'
    2020-09-11 07:14:36 gpg-agent[7656] DBG: ssh map file sid: 'S-1-5-21-2866614668-1482101499-365976279-1001'
    2020-09-11 07:14:36 gpg-agent[7656] DBG: ssh IPC buffer at 0x00770000
    2020-09-11 07:14:36 gpg-agent[7656] ssh request handler for request_identities (11) started
    2020-09-11 07:14:36 gpg-agent[7656] no running SCdaemon - starting it
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK GNU Privacy Guard's Smartcard server ready
    2020-09-11 07:14:36 gpg-agent[7656] DBG: first connection to SCdaemon established
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> GETINFO socket_name
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- D C:\Users\avemilia\AppData\Roaming\gnupg\S.scdaemon
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: additional connections at 'C:\Users\avemilia\AppData\Roaming\gnupg\S.scdaemon'
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> OPTION event-signal=0x00000280
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> SERIALNO
    2020-09-11 07:14:36 gpg-agent[7656] SIGUSR2 received - updating card event counter
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- S SERIALNO <SERIALNO>
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> GETINFO card_list
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- S SERIALNO <SERIALNO>
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> SERIALNO --demand=<SERIALNO>
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- S SERIALNO <SERIALNO>
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> GETATTR $AUTHKEYID
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- S $AUTHKEYID OPENPGP.3
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> GETATTR SERIALNO
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- S SERIALNO <SERIALNO>
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> READKEY OPENPGP.3
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_000002C4 <- [ 44 20 28 ... ]
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> GETATTR $DISPSERIALNO
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- S $DISPSERIALNO <DISPSERIALNO>
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:36 gpg-agent[7656] ssh request handler for request_identities (11) ready
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 -> RESTART
    2020-09-11 07:14:36 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:37 gpg-agent[7656] DBG: ssh map file 'WSLPageantRequest'
    2020-09-11 07:14:37 gpg-agent[7656] DBG: ssh map handle 0x00000298
    2020-09-11 07:14:37 gpg-agent[7656] DBG:           my sid: 'S-1-5-21-2866614668-1482101499-365976279-1001'
    2020-09-11 07:14:37 gpg-agent[7656] DBG: ssh map file sid: 'S-1-5-21-2866614668-1482101499-365976279-1001'
    2020-09-11 07:14:37 gpg-agent[7656] DBG: ssh IPC buffer at 0x00770000
    2020-09-11 07:14:37 gpg-agent[7656] ssh request handler for sign_request (13) started
    2020-09-11 07:14:37 gpg-agent[7656] new connection to SCdaemon established (reusing)
    2020-09-11 07:14:37 gpg-agent[7656] DBG: chan_0x000002c4 -> SERIALNO --demand=<SERIALNO>
    2020-09-11 07:14:37 gpg-agent[7656] DBG: chan_0x000002c4 <- S SERIALNO <SERIALNO>
    2020-09-11 07:14:37 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:37 gpg-agent[7656] DBG: detected card with S/N <SERIALNO>
    2020-09-11 07:14:37 gpg-agent[7656] DBG: chan_0x000002c4 -> SETDATA [...]
    2020-09-11 07:14:37 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:37 gpg-agent[7656] DBG: chan_0x000002c4 -> PKAUTH OPENPGP.3
    2020-09-11 07:14:37 gpg-agent[7656] DBG: chan_000002C4 <- [ 49 4e 51 ... ]
    2020-09-11 07:14:37 gpg-agent[7656] starting a new PIN Entry
    2020-09-11 07:14:37 gpg-agent[7656] DBG: connection to PIN entry established
    2020-09-11 07:14:45 gpg-agent[7656] DBG: chan_000002C4 -> [ 44 20 7e ... ]
    2020-09-11 07:14:45 gpg-agent[7656] DBG: chan_0x000002c4 -> END
    2020-09-11 07:14:48 gpg-agent[7656] DBG: chan_000002C4 <- [ 44 20 b3 ... ]
    2020-09-11 07:14:48 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:14:48 gpg-agent[7656] ssh request handler for sign_request (13) ready
    2020-09-11 07:14:48 gpg-agent[7656] DBG: chan_0x000002c4 -> RESTART
    2020-09-11 07:14:48 gpg-agent[7656] DBG: chan_0x000002c4 <- OK
    2020-09-11 07:15:33 gpg-agent[7656] DBG: chan_0x00000294 -> OK Pleased to meet you
    2020-09-11 07:15:33 gpg-agent[7656] DBG: chan_0x00000294 <- GETINFO pid
    2020-09-11 07:15:33 gpg-agent[7656] DBG: chan_0x00000294 -> D 7656
    2020-09-11 07:15:33 gpg-agent[7656] DBG: chan_0x00000294 -> OK
    2020-09-11 07:15:33 gpg-agent[7656] DBG: chan_0x00000294 <- BYE
    2020-09-11 07:15:33 gpg-agent[7656] DBG: chan_0x00000294 -> OK closing connection
# Remote
Prepare for session:
    ❯ gpgconf --kill all
    ❯ rm ~/.gnupg/*log
    ❯ gpg-connect-agent updatestartuptty /bye
    gpg-connect-agent: no running gpg-agent - starting '/usr/bin/gpg-agent'
    gpg-connect-agent: waiting for the agent to come up ... (5s)
    gpg-connect-agent: connection to agent established
    OK
<gpg-agent.log> after session:
    2020-09-11 07:14:02 gpg-agent[105576] listening on socket '/run/user/1000/gnupg/S.gpg-agent'
    2020-09-11 07:14:02 gpg-agent[105576] listening on socket '/run/user/1000/gnupg/S.gpg-agent.extra'
    2020-09-11 07:14:02 gpg-agent[105576] listening on socket '/run/user/1000/gnupg/S.gpg-agent.browser'
    2020-09-11 07:14:02 gpg-agent[105576] listening on socket '/run/user/1000/gnupg/S.gpg-agent.ssh'
    2020-09-11 07:14:02 gpg-agent[105577] gpg-agent (GnuPG) 2.2.23 started
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK Pleased to meet you, process 105574
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- RESET
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- OPTION ttyname=/dev/pts/1
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- OPTION ttytype=xterm-kitty
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- OPTION display=:0
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- OPTION xauthority=/home/ave/.Xauthority
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- OPTION putenv=DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- OPTION lc-ctype=en_US.UTF-8
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- OPTION lc-messages=en_US.UTF-8
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- updatestartuptty
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 -> OK
    2020-09-11 07:14:02 gpg-agent[105577] DBG: chan_10 <- [eof]
    2020-09-11 07:14:47 gpg-agent[105577] socket file has been removed - shutting down
    2020-09-11 07:14:47 gpg-agent[105577] gpg-agent (GnuPG) 2.2.23 stopped
    2020-09-11 07:14:48 gpg-agent[105666] listening on socket '/run/user/1000/gnupg/S.gpg-agent'
    2020-09-11 07:14:48 gpg-agent[105666] listening on socket '/run/user/1000/gnupg/S.gpg-agent.extra'
    2020-09-11 07:14:48 gpg-agent[105666] listening on socket '/run/user/1000/gnupg/S.gpg-agent.browser'
    2020-09-11 07:14:48 gpg-agent[105666] listening on socket '/run/user/1000/gnupg/S.gpg-agent.ssh'
    2020-09-11 07:14:48 gpg-agent[105667] gpg-agent (GnuPG) 2.2.23 started
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK Pleased to meet you, process 105664
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- RESET
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- OPTION ttyname=/dev/pts/2
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- OPTION ttytype=xterm-256color
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- OPTION putenv=DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- OPTION lc-ctype=en_US.UTF-8
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- OPTION lc-messages=en_US.UTF-8
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- updatestartuptty
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 -> OK
    2020-09-11 07:14:48 gpg-agent[105667] DBG: chan_10 <- [eof]
    2020-09-11 07:15:22 gpg-agent[105667] ssh handler 0x7f29eddcf640 for fd 10 started
    2020-09-11 07:15:22 gpg-agent[105667] ssh request handler for request_identities (11) started
    2020-09-11 07:15:22 gpg-agent[105667] no running SCdaemon - starting it
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 <- OK GNU Privacy Guard's Smartcard server ready
    2020-09-11 07:15:22 gpg-agent[105667] DBG: first connection to SCdaemon established
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 -> GETINFO socket_name
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 <- D /run/user/1000/gnupg/S.scdaemon
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 <- OK
    2020-09-11 07:15:22 gpg-agent[105667] DBG: additional connections at '/run/user/1000/gnupg/S.scdaemon'
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 -> OPTION event-signal=12
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 <- OK
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 -> SERIALNO
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 <- ERR 100696144 No such device <SCD>
    2020-09-11 07:15:22 gpg-agent[105667] ssh request handler for request_identities (11) ready
    2020-09-11 07:15:22 gpg-agent[105667] ssh request handler for sign_request (13) started
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 -> SERIALNO --demand=<SERIALNO>
    2020-09-11 07:15:22 gpg-agent[105667] DBG: chan_11 <- ERR 100696144 No such device <SCD>
    2020-09-11 07:15:22 gpg-agent[105667] DBG: no device present
    2020-09-11 07:15:22 gpg-agent[105667] starting a new PIN Entry
    2020-09-11 07:15:22 gpg-agent[105667] DBG: connection to PIN entry established
    2020-09-11 07:15:28 gpg-agent[105667] DBG: chan_11 -> SERIALNO --demand=<SERIALNO>
    2020-09-11 07:15:28 gpg-agent[105667] DBG: chan_11 <- ERR 100696144 No such device <SCD>
    2020-09-11 07:15:28 gpg-agent[105667] DBG: no device present
    2020-09-11 07:15:28 gpg-agent[105667] starting a new PIN Entry
    2020-09-11 07:15:28 gpg-agent[105667] DBG: connection to PIN entry established
    2020-09-11 07:15:30 gpg-agent[105667] DBG: error calling pinentry: Operation cancelled <Pinentry>
    2020-09-11 07:15:30 gpg-agent[105667] smartcard signing failed: Operation cancelled
    2020-09-11 07:15:30 gpg-agent[105667] ssh sign request failed: Operation cancelled <Pinentry>
    2020-09-11 07:15:30 gpg-agent[105667] ssh request handler for sign_request (13) ready
    2020-09-11 07:15:30 gpg-agent[105667] DBG: chan_11 -> RESTART
    2020-09-11 07:15:30 gpg-agent[105667] DBG: chan_11 <- OK
    2020-09-11 07:15:30 gpg-agent[105667] ssh handler 0x7f29eddcf640 for fd 10 terminated
[0] <https://dev.gnupg.org/T5062>