Self-Host relay server over https

I understand that syncthing uses a special port for sync (22067) and it does not support syncing via https. Is that true?

I saw on https://relays.syncthing.net/ that 141.14.27.100:443 uses port 443 and it is the relay that is supposed to transfer the most data.

So if it is possible to run a relay on port 443, does it require special conditions?

I am using caddy to host applications behind a domain with https Will adding a relay on port 443 be able to go through caddy?

Can anyone shed some light on this issue?