What clients work well with such relays?
https://relays.land/ now has an option to create moderated relays.
Moderated relays accept any events, but events only become publicly visible when manually approved by a moderator. Approval can be given either through the relay web dashboard or using NIP-86 methods.
Is this what was needed for moving the bitcoin-dev mailing list to Nostr?
Discussion
https://jumble.social/ is the best for now, but we're still early.
https://coracle.social, https://yakihonne.com and others can also be used to just browse.