Change the ssh port to something with 4-5 digits, disable ssh password Auth and use certificates only, don’t expose any port other than ssh and 443.
If you’re paranoid, use cloudflare as a proxy and set the VPS firewall to only accept incoming traffic from cloudflares ip list.
That’s about it really.
This will work, but is not as nice as the official way to do it via a config file, as described by another comment here.