If when trying to connect via SSH from a Mac, the SSH client returns the error:

Unable to negotiate with 111.222.333.444 port 22: no matching host key type found. Their offer: ssh-dss, ssh-rsa
In the terminal of the Mac where the error occurs, run: 
nano ~/.ssh/config
And in the file that opens, add: 
# SSH Host Configs 
Host 111.222.333.444 
HostKeyAlgorithms ssh-ed25519, ssh-rsa 
PubkeyAcceptedAlgorithms ssh-ed25519, ssh-rsa
where, 111.222.333.444 is the IP address or hostname of the server specified in the terminal when connecting.