They tried:
"This project is an Electron-compatible app shell for creating desktop apps based on Gecko, the rendering engine used in Firefox."
https://github.com/mozilla/positron
but they failed:
"As noted in the blog post Positron Discontinued [1], this project has been discontinued. The source remains available, and you're welcome to reuse it."
[1] https://mykzilla.org/2017/03/08/positron-discontinued/
That's exactly what I meant by false starts and head fakes.
In fact, xulrunner was another much earlier attempt at developing an Electron-like platform, but Mozilla's heart just wasn't in it, and they didn't care about or adequately support third party developers who were trying to develop applications with it, like TomTom Home for example (which I worked on).
Xulrunner was never meant to be a platform for desktop or embedded apps the way WebKit was -- its singular purpose was to support the desktop version of Firefox.
Which is exactly how Thunderbird got into the hopeless dead-end situation it's in right now. Its best move would be to switch to Electron, which is impossible only because of the obvious political reasons.
There's no reason to expect Mozilla to ever support any other Electron-like platform any better than they did xulrunner.
but they failed: "As noted in the blog post Positron Discontinued [1], this project has been discontinued. The source remains available, and you're welcome to reuse it." [1] https://mykzilla.org/2017/03/08/positron-discontinued/