Hello!
Pardon me if it seems you keep answering the same questions 
but I have read through all the results for Umbrel and BTCPayserver but I don’t see my use-case - unless I am misunderstanding…
I have Umbrel at home, installed BTCPayserver, set up store and app, and it works.
Now I want to access just the app from an iPad remotely at my brick and mortar store. I tried opening the “Public node info” onion address found in Stores/Payment Methods/Lightning through Tor, but it keeps failing. I don’t see an onion address in the Apps settings.
I did read https://jorijn.com/installing-nginx-reverse-proxy-with-ssl-certificate-umbrel-btcpayserver/ but it doesn’t seem to be what I want to do - I just want to access the app. Unless that is the only way?
Thanks!
Alex