It used to be centered around XUL, and there was even a sort of proto-electron in the form of xulrunner and the related Prism project, but they were all dropped years ago and XUL itself has been deprecated and is being steadily replaced.

There might've been a window somewhere in there where turning XUL/Gecko into a Qt style application toolkit could've been an option, but I think we're well past that point now.

Because Electron is a neverending toxic pile of shit.

You still need to render that js/html with something. Chromium based on skia. IIRC Firefox was based on it as well, but migrated from it.