I have been running AOSP-based LineageOS and now GrapheneOS for more than a decade now. While some apps are restricted to Google-certified operating systems, most are definitely not. I can use my countries eID apps and my banking app without issue. The only thing not working is nfc payments (since they are limited to Google Wallet)

It doesn't matter if it's only some apps if those apps are critical. MyGov in Australia for example requires Play Integrity or it crashes. Your government's app does not... for now.

The grip of Google, Microsoft and Apple are tightening. Microsoft's TPM requirements for Windows 11 are ostensibly for security, but they're also a mechanism to enforce hardware/software integrity and authentication. Google wants to extend their integrity APIs to Chrome and I doubt Microsoft would object to implementing something similar.

Soon enough computing and the web may end up segregated, with there being devices authenticated and controlled by a central authority and those that are not. In a lot of ways this is already the case, I can't access the 4K Netflix streams I'm paying for on Linux because of DRM and using anything other than stock Chrome can often get you flagged for annoying captchas. But it can get so much worse than that.