I don't get excited about new OSs unless they're FOSS. It sounds like an ideological take, but it's not: When an OS is not FOSS, they either succumb to the wrong incentives and lack of care (Windows) or just become a walled garden (MacOS). From what I've seen from, say, Visual Studio Code (FOSS version), or Chromium, or other such projects, is that a large company open-sourcing the core of their product can only yield positives over the alternative (fully closed) solution.
Fully FOSS would be sick, partially would be useful. Closed and ad-ridden, driven by wrong incentives and run by a company with zero sense for privacy (see their Facebook product) and a love for hype (see their AI and Metaverse products that just about nobody wanted?), I don't see this becoming very popular.