> That said, blocking all countries that you don't expect to talk to

All fun and games until you find yourself on travelling in Asia and you need to connect back home and forgot you blocked half the world.

As for "other processes", we're talking about SSH on this thread. If you've got other processes then that falls into on-host/upstream filtering via firewall area of security. Regarding "unknown vectors", as I said, patching, no amount of IP blocking will help you with that.

If you really want to talk about "world's second easiest security fix" for SSH, that would be running a super-hardened bastion host and using SSH ProxyJump.