You can't grant yourself admin access with the official build. Only the Graphene devs have the ability to push changes to the OS on your phone. Yes you can fork the software and build a version with your own signing key, then wipe your phone and install your custom build and thereby take back control, but then is that really still Graphene?
I think it's fair to say that that's at least borderline anti software freedom, even if it's true they have good security reasons for doing things that way.
Thinking about possible ways they could retain the same security properties without impinging software freedom... maybe there's a way they could make the root of trust default to a signing key embedded in the device's own secure hardware? Then by default that key could sign Graphene's own signing certificate to allow them to push updates, but the user would retain the ability to revoke that signature and sign someone else's certificate instead (or their own certificate) if they decided they didn't trust Graphene anymore, or wanted to give themselves root.
> I think it's fair to say that that's at least borderline anti software freedom
Then you don't understand software freedom either.
Software freedom doesn't mean AT ALL that random projects on the Internet MUST implement the features YOU want. Never, not at all, it's not borderline, it's not up to debate.
Software freedom is about being able to use the software the way you want, as in "you get access to the sources, you modify them, build them and run them". You can do that with GrapheneOS (well except for the binary blobs situation, but that's not in GrapheneOS' hands at all). Software freedom is NOT about GrapheneOS giving you root access on official builds because you want it. And it's also NOT about GrapheneOS installing Doom on the official builds because I want it.