Sure, the lockdown situation is worse than things are currently. You're likely to need per-device hacks that unlock it and enable freedom for users.

Even in that scenario though, ARM devices use standards too. There's a reason I can generally pick up any Android device and know what needs to be done to build my own OS for it. We just lack tooling that makes that incredibly easy and lack maintainers who want to make those devices work with the mainstream linux kernel.

Having open devices though (outside of Apple) is still my bet. We still need to make that process smoother but that just means there's lots of low hanging fruit :)