On the client side, add the following to .ssh/config:
HostKeyAlgorithms=+ssh-dss KexAlgorithms +diffie-hellman-group1-sha1,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1 PubkeyAcceptedKeyTypes +ssh-rsa
or
PubkeyAcceptedAlgorithms +ssh-rsa
I'm not sure what impact this has on security.