So you’re suggesting MS will somehow block non-Windows OSes from installing, even on hardware like loose mainboards for building your own PC with, or even on barebones mini PC kits or certain laptop SKUs, which don’t ship with an OS installed to begin with and expect the user to install it themselves? I mean, unless something extreme happens like changing the entire PC platform to be like the current Macs, that won’t be feasible.
Also, doing that would kill the Steam Deck which I doubt Valve would take sitting down.
Even older dGPUs like the R9 270/270X or 280/280X, hell, even the R9 290/290X or 390/390X (R9 390/390X is just a faster 290/290X which ships with 8GB VRAM as standard issue), while admittedly pushing it a little, will also work fine for most indie titles and even truly ancient (as in DX9-era and earlier, think stuff like Silent Hill 2 which launched in 2002 for the PC) AAA stuff, you’ll just need to manually enable a compatibility toggle for GCN1 or GCN2 cards to work with AMDGPU in DIY distros like Arch or Gentoo while last time I thought some prebuilt distros like Fedora enabled it by default.
These are the compatibility toggles you’ll need to set in kernel parameters for GCN1 and GCN2 cards to work with AMDGPU if they’re not set already. GCN3 and newer natively supports AMDGPU without needing said toggles.