Gregor Mueckl

No, Lightning and Enigmail are the only two addons in the affected Thunderbird installation.

Below is what is displayed in the Error Console after startup. Is this helpful in any way? Do you need more info on any part of this? WebExtensions: Loading packed extension from /home/gregor/.thunderbird/4tppmusp.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi ext-legacy.js:157 WebExtensions: Loading add-on preferences from /home/gregor/.thunderbird/4tppmusp.default/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi ext-legacy.js:190 WebExtensions: Firing profile-after-change listeners...

Doing this does not work. The behaviour stays unchanged. Something is that specific column and it ends up quite wide on screen. The curious part for me is that the column visibly pops into view seconds after the message list is already shown and seems to be fully populated with data. Some kind of background initialization seems to be messing with column visibility.

Lightning Addon makes Enigmail/OpenPGP column appear at program start