That is essentially it as far as my understanding goes.
Google Wallet currently will not run on a fully updated grapheneOS.
Specifically it complains:
"Your device doesn't meet tap to pay security standards. It may be rooted or running uncertified software."
Which is fair. But something that actually works would be nice. I can keep extremely tight control on the NFC stack by toggling NFC with a quick access icon.
Not something I use very often, but not getting locked out of specific, not all, financial rails is one of those things that feels like it rubs up against the perpetual friction that the US founders, framers, whatever; didn't enshrine economic freedom in the same way as speech.
And maybe that's a libertarian fantasy. Idk. Seems worth thinking about for five seconds tho.
Bringing it back to reality. There are an incredible number of issues with trying to set up some kind of a competing service to Google Wallet to the extent that you might as well just go start a bank. And companies like simple have tried that and ended up bought by other banks at the end of it. And they weren't even trying to do anything other than offer people a banking app that wasn't total crap back in the day.
So realistically Google wallet or anything like that is not something I expect to use on a graphene OS phone until the graphene OS Motorola device comes out in the next few years. And that is entirely speculation that services like Google Wallet might be able to work on that device. But honestly it's the only real hope I personally hold for getting access to Modern payment systems on a secure device.