Firefox to become first mobile browser to support desktop extensions later this year
Prepare your Firefox desktop extension for the upcoming Android release
And yet they've turned their back on *Android tablet users and refuse to support the tab bar.
https://github.com/mozilla-mobile/fenix/issues/2344
Ridiculous. Only reason I switched to Vivaldi
iOS/iPad OS is relatively much easier to develop and it's a completely different branch from Android as it's a skin on top of Safari Web View. All other platform use their own Quantum/Gecko Engine.
if you want to get things done, use a real OS and not an artificially limited mobile OS.