Rated 2 out of 5 stars

Don't work with PGP.

Edit: Too bad, sad to know that the developer does not support the use of PGP. I believe it would be of utmost importance for this add-on limitation to be presented on the add-on's download page.

ATN reviews are for rating how well the add-on performs its intended function, not for dinging it for things it is not designed to do:
https://addons.thunderbird.net/review_guide

EDIT: I would love to support PGP, but it is HARD and will likely require completely rearchitecting how the add-on works. I don't get paid for this work and I have a full-time job, so it's not like I can spend limitless hours working on the add-on. But of course it's open-source software, so if the feature is that important to you then you are welcome to add it yourself!