xpra started failing for me with this error:
xpra initialization error: cannot get IPv4 address of ('wpc', 22): [Errno -2] Name or service not known
This seems due to using "paramiko" instead of actual ssh, which means any ssh configuration is suddenly silently ignored (in this case, a host alias to go via a proxy). There should at least be a warning that ssh is not used and thus any settings in .ssh/config are ignored, and also a hint on how to get the old behaviour back. Even better would be some kind of automatic fallback on connection issues.
As there might also be more subtle failures (like suddenly not using a privacy-protecting VPN) I would however suggest to reconsider the change in default ssh client in general, until either paramiko can parse .ssh/config or at least there are some basic checks on .ssh/config not containing anything critical. Or until a major version bump...
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2020