You right. With some exploration I’ve found the real problem is nostr:npub1aghreq2dpz3h3799hrawev5gf5zc2kt4ch9ykhp9utt0jd3gdu2qtlmhct still hasn’t added https (come on guys), blocking remote btcpay. 

FWIW nostr:npub126ntw5mnermmj0znhjhgdk8lh2af72sm8qfzq48umdlnhaj9kuns3le9ll makes this possible and it’s not hard. 

With an umbrel setup it’s problematic. Best potential I can see is using cloudflare tunnels tied to a domain name which points to an app on umbrel. Not sure how well it works in practice however.