GoPay

It was fine, until one day "error connecting to external server" when trying to activate a ticket. This behavior persisted for more than 24 hours, and I uninstalled it afterward. Several days later I tried again and it still wasn't fixed.

Requires a Polish phone number, so it wouldn't work for me when on a trip to Poland.

So this is yet another travel app that I can't use with my phone number. The first step to access this app is to put in your phone number. Polish phone numbers have 9 digits. Norwegian phone numbers have 8. So it just tags my input as an error (yes I did add the 47 before the actual number, nevertheless). On to the next one.