Open hardware is a somewhat different topic than FOSS. Yes, lots of hardware is closed and proprietary blogs are unfortunately still needed.

But that doesn't mean Linux or OSS is going away anytime soon. There's more Linux systems in the world than every other OS that's ever existed combined. For a large portion of the world a Linux (Android) device is the only computing device they've ever used. Even in developed countries, desktops are less and less relevant and mobile devices are #1, and outside a few select countries, that means Linux (Android).

And Linux is gaining steam if anything thanks to AI, since most of the infrastructure related to producing LLMs runs only on Linux. No one's running Windows server on a 300k node cluster.

And to address your point directly, installing Linux on non-Linux hardware is still better than it's ever been. More hardware is compatible than ever before (I've been running Linux since the early 2000's) and while running non-Android Linux on phones isn't great, even that is better than it used to be.

But yeah, we probably won't ever reach the "whole stack is open top to bottom" future that people like RMS dreamt about...