Does modifying ~/.ssh/config
to contain the exception work?
Host somehost.example.org HostKeyAlgorithms +ssh-dss
Note, that whatever infrastructure you're working with urgently like a hole in the head needs to be patched. This isn't optional, at this point it's serious negligence. You wouldn't leave the office unlocked because the door got too old to lock? This is just as unacceptable, this needs addressed like today.