The current best practice is to use ed25519 keys with ssh.
If you have some old ssh servers still using RSA host keys you might want to update those to use ed25519 host keys.
This is how to generate new ed25519 host keys for your SSH server:
ssh-keygen -q -f /etc/ssh/ssh_host_ed25519_key -N "" -t ed25519
sshd_config to use the new key and decomission the old ones.