Ok #asknostr advise me of a good FREE relay. The one you like best.
I'd say it's nostr.mom, but the Chinese spam there is getting annoying.
Discussion
Unfortunately, when this is the question, the result is the inevitable centralization of Nostr around commodity relays.
A better question to ask is which clients implement the gossip model to discover notes on relays you don't know about.
Primal is a good client because it solves this problem at the caching layer.