So, you might be interested in https://github.com/SimulaVR/Simula . There have been a few examples of VR windows managers on Linux which don’t require an entire OS rewrite.
Is that the solution Meta will go w/? almost certainly not. But replacing a WM for a different “view” of your OS is a pretty common thing on Linux. (For some distros like Arch, replace isn’t the right word. You have to install whichever one you’d like from the beginning)