Comment 11 for bug 1585903

Bryan, see https://bugzilla.mozilla.org/show_bug.cgi?id=1423363

Thunderbird only does major releases based off Firefox ESR's. Firefox 52 ESR still supports GTK2 plugins besides Flash. Therefore, I was thinking it would be safer to drop the gtk2 dependency in the current Thunderbird Beta's or in the next major release which I believe will be Thunderbird 60 and so it will be too late for Ubuntu 18.04 (but not 18.04.1). (Earlier, 59 was scheduled to be the next ESR and might have been early enough.)

We could
1. look at doing the change anyway in Ubuntu 18.04, or
2. ship a Thunderbird Beta, or
3. just wait for 18.04.1 and 18.10 to drop gtk2 from the default install, or
4. not include Thunderbird in the default install

See https://wiki.mozilla.org/RapidRelease/Calendar (note that a new major Thunderbird release is expected to a bit late compared to the Firefox ESR release)