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More than just two. WebOS would probably fall into this category too. Which would also then include LuneOS.

Electron probably deserves a mention too (since you raise the point of PWAs).

I always though webOS didn't actually use the web stack for its applications but after some reading, I guess it does, though you can also make apps using Qt.

Firefox OS still lives on as the decently successful KaiOS, for really cheap feature phones. Those things are vastly popular in some countries.

There's some discussion about whether it has become abandonware though. Kai hasn't said anything since 3.0 dropped.

Besides that, we just made the browser the OS to a large extent. Want to do some coding? Open browser, use an online IDE, etc.