Has someone tried iCard app for digital payments? There is a option to pay with NFC with the balance loaded in the app. If the apps works with GrapheneOS this can be an alternative to Google Pay. I can't try the app right now but if someone wants to do that and share their experience is welcome. I don't know if the service works outside Europe.
I wouldn't load much money here, but for everyday expenses should be fine. Here is the link to their website.