Unable to negotiate with 192.168.1.99 port 22: no matching host key type found. Their offer: ssh-dss
It looks like the DSS option is not considered secure so when connecting from newer Linux systems to an older one you will get the above error.
It can be fixed (but you should consider upgrading your SSH daemon):
ssh -oHostKeyAlgorithms=+ssh-dss firstname.lastname@example.org