This is the problem: it was a cat and mouse game always. I managed even strong integrity with keybox stuff and so on. Yes it is possible. But if you really need to do send money or e. g. want to pay with NFC, it gets rather stressful. Yes, I got everything working (Note 10 pro on LOS 23), but never longer than a few month.
I just decided to completely stop paying with NFC. I always carry a few cards with me and Wero is already working in a few spots, which requires just your banking app and a working camera.
I don't even have Google Wallet installed anymore.
There are alternatives to Google Pay in Europe which work on GrapheneOS and it's likely most of those work on a production (user) build of LineageOS with a locked bootloader too. Only a few are specifically permitting GrapheneOS, and those would also be willing to explicitly permit a subset of LineageOS devices too. They'd need to start keeping a bit more of the standard security model and features intact which wouldn't be a large change. They'd mostly just need to make full production builds and start officially supporting locking. Having the privacy and security improvements done by GrapheneOS is in no way a requirement for compatibility with those financial apps.