Yes, the mobile app supports third-party servers, though I wouldn't call it complicated.
If you want to join a room, all you do is type/paste the full URL to it instead of just the name. "Open in App" functionality will also work regardless of the server.
If you want to host one on a third-party server, you just go into the options and replace the "https://meet.jit.si" address with one of the third-party server. Then when you create a room, it will use that server.