ssh connections 'No existing session' error

[totaam]

Is caused by a paramiko bug: paramiko/paramiko#1390
I am seeing this with Fedora 34 and ssh keys added via gpg (on a yubikey).

The fix: paramiko/paramiko#1687 has been waiting for over a year 😞

The solution with xpra is to turn off agent and / or keys authentication:

xpra --env=XPRA_SSH_KEY_AUTH=0 --env=XPRA_SSH_AGENT_AUTH=0 attach ssh://host/

[totaam]

Works-for-me(tm).

Just needs testing on more platforms with more ssh servers.
(Difficult to backport - probably just replace the whole ssh.py file)