Comment by Aachen

GrapheneOS doesn't solve the attestation problem though. If you compile it from source, the attestation still breaks (namely, you have to convince vendors that use attestation to trust your key). In practice, it does not allow you to run your code on your device anymore than stock Android with Google services does. At best, if GrapheneOS' build is reproducible, you can view the source code online and know that there isn't anything else in the blob you load onto your device

Source-available isn't quite the same as having the software freedoms (use, study, modify, share) where you can modify the code or inspect what the various third-party apps are doing on your device. I can currently look into /data/data/any_app and modify preferences, view what telemetry is queued up, remove gigabytes of cache files... all that goes away with a GrapheneOS installation that passes attestation. They want to appear legitimate to app vendors and so comply with Google's rules about what data is accessible to users; otherwise, they'd never convince anyone to add their attestation keys to the allowlist. You need to be on a closed device before those vendors put you on the allow list (and you probably need to sell at least a million devices before they bother to consider you). The concept of attesting your phone is fundamentally antithetical to open source