After a few months of transition, I've now moved all of my PWAs over from Firefox to Vivaldi.

I'm still using FF as my main browser for the time being, but its PWA support has caused me too many problems, and they don't seem to have any desire to fix them.

For example:
PWAs often crash on launch: https://bugzilla.mozilla.org/show_bug.cgi?id=1974078
PWA notifications can't be opened: https://bugzilla.mozilla.org/show_bug.cgi?id=1880000
Switching between light/dark mode breaks PWAs display mode: https://bugzilla.mozilla.org/show_bug.cgi?id=1933470

And many smaller things like choppy animations, occasionally PWAs completely hang and don't load until I restart the app or even the browser, notifications don't support images and many other features, and newer manifest properties aren't supported at all (eg display: override).

This is shame because I mostly like using FF, it does a lot of things well (extensions on mobile and very good Linux support being two of my favourites), and browser engine diversity is good to have and lacking, but they really need to get somebody to work on PWAs again.