> You can't use the software in the way you want if it uses hardware backed cryptography to block you from doing so.
You can use the software the way you want, from sources. If I run an open source server at home, it does not give you the right to enter my house and come reboot my server, does it?
> This is completely infeasible for 99% of the population
Sure, it isn't. Still that's what software freedom is.
> If you technically have a freedom but have no practical way to exercise it, it may as well not exist.
I disagree, I'm very happy that free software exists.
> I think it's debatable at that point whether you'd still be running Graphene
It's not: you're running a fork at that point. That's precisely how free software works.
> And if exercising your freedom requires you to stop running Graphene and start running something else, is it really fair to say Graphene itself supports that freedom?
Yes! Again that's precisely what software freedom is about! When you run GrapheneOS, you have the freedom to fork it and run it however you want. When you run Windows or macOS, you don't.
> If you're still not convinced, consider what would happen if companies started using remote attestation to verify you're running the official GrapheneOS build and block forks...
Well GrapheneOS would still be free software?!?!? It's the software from those companies that wouldn't be. I hate remote attestation as much as the next person, and typically banks absolutely suck because they love doing that kind of bullshit. But because banks suck does not mean that GrapheneOS is not free software?
Note that I am not trying to contradict you for the sake of it. I believe too few people understand how open source works, and that is a pity because it is important to understand it. When I open source some code I wrote, I make it available for people to do whatever they want with the code. I don't give them ANY RIGHT on the products I sell (even if those products are running said open source software) or on the feature I implement.
Too many people believe that because it's open source, they have a right to tell the authors what features they should implement. This is wrong. You want root access on your GrapheneOS? Go fork it. I don't want it, I am happy with GrapheneOS. If GrapheneOS gave me root access, I would fork it to remove it. And that would still be free software!