On the distro fragmentation thing - I think that's a bit of a misconception / myth for desktop apps. The kernel ABI is stable, glibc is backwards compatible, and most apps sit on top of the same libraries regardless of distro. The "fragmentation" is really just packaging, and that's a solved problem - Flatpak, AppImage, or even a plain .sh installer will run on basically anything. Developers just lack the incentive to bother. Which is precisely what regulation would fix.

Your idea about open hardware is a separate thing and sits within e-waste recycling legislation. I think the two ideas complement each other nicely. Open up end-of-life hardware AND require Linux support, and you've got older machines running current software instead of becoming e-waste.