yep, like a mesh network, that make sense.

But a nostr relay for example still needs a domain on clearnet or an .onion on tor network, will it always be the case?

The only thing that makes sense is for nostr to create its own network like tor, i2p, cjdns and probably many more that nobody has ever heard of.

But "nostrnet" won’t replace clearnet (DNS+IPv4+IPv6) where 99.99% of all internet traffic happens.

It’s just going to be another tiny network that only a few people care about.