Eh kind of but you are mixing the OS with the application framework to make it look like more things exist.

PWA for ChromeOS, Flutter for Fuchsia (but yes it is multi-platform), JetPack Compose for Android (but does have some multi-platform stuff coming out).

So really it's three.

PWAs, Flutter, and Jetpack Compose.

Of which I think PWAs rightly exist alongside a native solution.

Flutter is sort of the odd one out and not sure where it will be long term. Although it's becoming more clear Fuchsia is probably going to be for IoT devices, so I could see Flutter being used as an application framework for them (which IMHO makes a lot of sense.)