I'm running GrapheneOS too and while I've experienced the same, I'm dreading the day any of my banking apps update and suddenly start demanding full Play Integrity API support (GrapheneOS only has Basic) causing them to fail to open. Hasn't happened yet but it could.

It always feels like my phone experience is just a pleasant intermezzo. My banking app (ABN Amro) works, government apps (DigiD) work, everything just works, and I get security and a certain degree of distance between me and Google. I can use F-Droid to install useful apps, and incidentally use Google's app store for apps I need because the rest of the world uses them. GrapheneOS rocks.

Borrowed time. I hope not, but that's the prevailing feeling.

Happened to me. Stopped working on GrapheneOS because of some goddamn check they make, but still runs on an outdated /e/OS signed with the Google test keys (i.e. without a proper secure boot).

The real fight is to prevent companies (like those banks) to do that kind of shit. And to force manufacturers into allowing us to install alternative systems, instead of preventing unlocking/relocking of the bootloader for instance).

If that happens you could buy a cheap Android like a Moto G for that indispensable banking app and keep using your GrapheneOS device for everything else. Not ideal, but many of us have old devices lying around that can be used for that.