AFAIK The Thunderbird developers never had anything to do with that extension and the extensions developer never hosted it on ATN or AMO and it only works in Unity. Maybe Gnome. I would have to boot up a LiveCD/USB and test. Thanks for pointing out bug 1599924. I think this one could be resolved as a duplicate.
Bug 1601319 Comment 5 Edit History
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AFAIK The Thunderbird developers never had anything to do with that extension and the extensions developer never hosted it on ATN or AMO and it only works in Unity. Maybe Gnome. I would have to boot up a LiveCD/USB and test. Thanks for pointing out bug 1599924. I think this one could be resolved as a duplicate. Also thanks for considering taking a stab at porting it.