Odd issue with SSH connecting to old systems

[Internaut]

I suspect this is a bit of an obscure one. I often need to SSH into boxes in the field that are reasonably old. For example, a Sun box I helped install in Kinshasa back in 2014. To deal with this, I have the following lines at the top of my SSH config:

PubkeyAcceptedAlgorithms +ssh-rsa,ssh-dss
HostKeyAlgorithms +ssh-rsa,ssh-dss

Since upgrading to Tahoe, I get the following error if I try to SSH anywhere without first commenting out these lines:

/Users/myname/.ssh/config line 1: Bad key types '+ssh-rsa,ssh-dss'.
/Users/myname/.ssh/config line 2: Bad key types '+ssh-rsa,ssh-dss'.

Clearly, Apple has gone gangbusters on older cryptographic tech! It's not critical - I can just run up a Linux virtual machine (or compose a suitably equipped Docker container), so I'm writing out of curiosity to see if anyone else has worked around the problems by other means. I do have the privilege of working with a real SSH nerd, though he knows nothing of macOS, so he might well have a suggestion for options when running the SSH command.

 

[PotentPeas]

You could try installing the "openssh" package through Homebrew. It installs another ssh binary at /opt/homebrew/bin/ssh (which you could make the default by messing with the PATH environment variable) which might have more forgiving behavior for old encryption methods?