I use selfhost.de (they register domains via united-domains for you) who are specialized on self-hosting in Germany and offer a wide variety of options on how to connect a domain using dynamic DNS.
the lemmy.world guy had to upgrade servers at least twice during the boom
It’s their fault, though. You could either throw money at it to gain more and more power over users, or you embrace the federation and disable new registration at a certain amount of users.