I've been using GNU/Linux as my phone OS for the last 18 years on several devices, enjoying "normal payloads of tools & scripts". Aside of a short time around 2017-2019 I never carried and relied on any other phone. It's not some wishful fantasy, it already exists and works.
I do see remote attestation as a grave threat not just to mobile phones, but to general purpose computing as a whole (well, aside of offline use cases perhaps). It creeps in slowly, but I'm hopeful we can still fight it off.