Fullscreen mode only working on HTTPS is nothing to do with worker mode. Many browser features require secure hosting now, including fullscreen mode, regardless of worker mode.
Well, full screen mode does not work with worker mode on, if I disable it, full screen works. Same device, soobviously it has something to do with worker mode.
As for performance. Game works normally without worker mode, with worker mode on crawls at 2 FPS.
Issue was 20 sprites on top of each other. Changing that fixed it, but it did not need to be fixed without worker mode on, game worked fine even with those 20 sprites on top of each other.
I know this has something to do with devices in question, but between this and complaints about webview I think things are not as fine as they may seem. Let's say you make a soccer game, and soccer is popular in South America. You are gonna have a disproportionately large number of players with low end and very old devices. Even in the US, I have friends who cannot test my game because of these things and their phones are about 2 years old.