I use Fountain (just installed today and loving it), Tweetoshi, Alby and of course Nostr, where LN is not supported natively, but it's written all over it.

We still have a long way to go with LN adoption, but the critical mass has been exceeded and it's inevitable. We'll get there before we even know it. Apart from payments, I think another killer feature of LN is going to be the login functionality, replacing the traditional login/password model.