Multiple Server Host Key Algorithm Support

Serv-U already supports the rsa-sha2-512 and rsa-sha2-256 host key algorithms. You can check by going into the session list and looking at SFTP sessions. It is shown as "public key protocol".
Combine that with ssh -o HostKeyAlgorithms=xyz and you can verify for yourself.

OpenSSH 8.9 unfortunately no longer supports RSA certificates without configuration modification. For many of our partners who transfer data to us via SFTP, such a configuration is very difficult to implement. We cannot simply exchange our RSA server certificate because it would have a negative impact on other SFTP accounts. The ability to implement multiple certificates is therefore urgently required!