Let's first collect all keys, assign a priority, sort, and only then send them back to ssh.

Well, I do not yet see a use case for this. The current rush towards PQC makes it unlikely that newer curves will get in widespread use. Iff we have a large application which requires this curves, we can reconsider,

It turned out that this does not make much sense.

We can simply change the arg type from number to string and use a value like 3072/20240101

I see the use to have an option to have a stricter "min-rsa-length", and which will be useful even in the future e.g. for 4096.

I think the current way is a good compromise. Turning this into a fatal error has also resulted in very many support cases.

For testing I have created a Gpg4win installer and only selected minimal installation and gpgme-json was there. Both in /bin and /bin_64.

Thanks all. It is a bug in Win32 OpenSSH. https://github.com/PowerShell/Win32-OpenSSH/issues/1953 it is already fixed. I think the issue will be resolved after the update is shipped. I could use ssh -T git@github.com as a workaround.

Well, not our bug... it's a kind of support question and answer:
This might help: https://stackoverflow.com/questions/3844393/what-to-do-about-pty-allocation-request-failed-on-channel-0

This does not look like a problem in GnuPG/gpg4win because gnupg implements the ssh-agent protocol and not the ssh server or client functionality. ssh tells sshd whether it shall allocate a PTY (Pseudo TTY). I don't use ssh with github but it is likely that you may only run commands (which don't require a PTY). Usually you would invoke a "git" command cia ssh.

Authentication succeed if I pressed enter after:PTY allocation request failed on channel 0

I try WinGPG 4.1.0, and I receive an error:
ssh git@github.com
PTY allocation request failed on channel 0