2.1.19 behaves (almost) the same:

• dirmngr does ignore /etc/hosts
• dirmngr is only resolving trough dns

SRV? _pgpkey-https._tcp.keyserver.example.com. (59)
SRV? _pgpkey-https._tcp.keyserver.example.com.localdomain. (71)
A? keyserver.example.com. (40)
A? keyserver.example.com.localdomain. (52)
AAAA? keyserver.example.com. (40)
AAAA? keyserver.example.com.localdomain. (52)
A? keyserver.example.com. (40)
A? keyserver.example.com.localdomain. (52)
AAAA? keyserver.example.com. (40)
AAAA? keyserver.example.com.localdomain. (52)

The command output changed slightly:

gpg2 --debug-level guru --search-keys example.com
gpg: enabled debug flags: packet mpi crypto filter iobuf memory cache memstat trust
hashing ipc clock lookup extprog
gpg: DBG: [not enabled in the source] start
gpg: DBG: chan_3 <- # Home: /tmp/gnupg-test
gpg: DBG: chan_3 <- # Config: /tmp/gnupg-test/dirmngr.conf
gpg: DBG: chan_3 <- OK Dirmngr 2.1.19 at your service
gpg: DBG: connection to the dirmngr established
gpg: DBG: chan_3 -> GETINFO version
gpg: DBG: chan_3 <- D 2.1.19
gpg: DBG: chan_3 <- OK
gpg: DBG: chan_3 -> KS_SEARCH -- example.com
gpg: DBG: chan_3 <- ERR 167772380 No name <Dirmngr>
gpg: error searching keyserver: No name
gpg: keyserver search failed: No name
gpg: DBG: chan_3 -> BYE
gpg: DBG: [not enabled in the source] stop
gpg: random usage: poolsize=600 mixed=0 polls=0/0 added=0/0

outmix=0 getlvl1=0/0 getlvl2=0/0

gpg: secmem usage: 0/32768 bytes in 0 blocks