What packages are OK to use with WebGL build? (Mutex.js:19 error persist)

I posted this bug two months ago (https://www.fusetools.com/community/forums/bug_reports/fuse_0854859__webgl_build_gives_errors) and a month ago it was marked as solved. However I haven’t seen a build that has it fixed yet. So I’ll just keep on posting.

My current version is 9.6.5478 .

I tried to remove basically everything from project file and still get:

Mutex.js:19 Uncaught Uno.Exception: Feature not supported in this backend

Project file:

"Packages": [
     // "Fuse.BasicTheme",
     // "Fuse.Themes",
     // "Fuse.Controls",
     // "Fuse.Reactive",
"Includes": [


And MainView.ux is just:


So is it that the fix haven’t been added yet or did it emerged again? Or what I’m doing wrong here?