Tested in virtual machines, amd64 and i386. I set up thunderbird with an existing gmail account and smoke tested various functionalities for a while (including enigmail, calendar, and linking large attachments with WeTransfer), and everything appeared to work as expected.
I tested the following packages (and their dependencies) from bionic-proposed:
thunderbird 1:68.2. 1+build1- 0ubuntu0. 18.04.1 1+build1- 0ubuntu0. 18.04.1 0ubuntu1~ 18.04.2
xul-ext-lightning 1:68.2.
enigmail 2:2.1.2-
Tested in virtual machines, amd64 and i386. I set up thunderbird with an existing gmail account and smoke tested various functionalities for a while (including enigmail, calendar, and linking large attachments with WeTransfer), and everything appeared to work as expected.