My initial suggestion within the Draft PR on Github was reusing NIP-05.

tl;dr: For a user, you do:

`ingwie@birb.it -> birb.it/.well-known/nostr.json?name=ingwie`

For a community:

`birb.it/someplace -> birb.it/.well-known/nostr-community.json?name=someplace`

Same idea, different layout. "someplace" IN the birb.it namespace - whilst "ingwie" AT birb.it (company, group, ...).