To improve user experience, Nostr clients typically pre-load several large relays. In fact, Nostr also supports using NIP-19[1] pointers to pass custom relay hints to the client, similar to the tracker in BitTorrent and Magnet. Furthermore, I believe that with Let's Encrypt now offering free and widespread IP certificates, domain dependency issues will be further alleviated on Nostr.
[1] https://nips.nostr.com/65