The problem of commerce over lightning isn’t a lightning problem, it’s a “bad money drives out good money” problem. With that said though, I bought prints from Argentina and a poster from the Midwest solely coordinated over Nostr and using lightning as the payment method. At a bare minimum, Lightning will very likely be an intermediate payment protocol between wallet, banks, custodians, and exchanges. Market solutions like Zeus and Phoenix are rapidly becoming more user friendly though, so it could go much further as well.