Yeah, this lives in the back of my mind too. I run debian on 11th gen intel, but with the non-free blobs included to make life easier. I've been meaning to try it without them, but it's too tempting to just get things 'up' instead of hacking on it.
RISKV has been a great step forward and I'd love to see it succeed but I'm also aware of the lack of open source architecture for GPU's or AI accelerators.
And sure, companies can choose not to share chip designs, but if you want an open-design CPU then you should be checking for that specifically and not just filtering by ISA. There exist such chips already, and I expect they'll catch up with AArch64 chips (in terms of being able to run desktop Linux) in <10 years, given the specs already include SIMD and the high-end chips have clock rates comparable to the oldest Windows-on-ARM laptops, like the 1st-gen Surface.