I had the issue where we had upgraded a system and as a result when I tried to SSH to another system which had not been upgraded I recieved the following error:
Unable to negotiate with XX.XXX.XX.XX: no matching host key type found. Their offer: ssh-dss
Turns out this is because OpenSSH has deprecated DSA keys by default.
The easy solution to these is to adjust or create an ~/.ssh/config file with the following information:
Host your-remote-host HostkeyAlgorithms +ssh-dss
This will enable access to the system that previously wasn’t allowed. Works for any SSH session including Rsync.