Limit the key exchange algorithms to those which are FIPS-approved.
Add or modify the following line in /etc/ssh/sshd_config
KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256
This rule ensures that only the key exchange algorithms mentioned
above (or their subset) are configured for use, keeping the given
order of algorithms.