Rated 5 out of 5 stars

EDIT: Nevermind, I got my smartcard to work following the instructions from https://wiki.mozilla.org/Thunderbird:OpenPGP:Smartcards

This extension is perfect, way better than the native GPG feature that was forced upon us in the latest version of Thunderbird.

The native GPG support is pretty much useless without smartcard support for private-key and public-key operations.

Who would trust to have a private key in a computer connected to the internet?

Well, I digress...

Is there any way to keep using your add-on, even after upgrading Thunderbird to newest versions?

Congratulations for your work!

This review is for a previous version of the add-on (2.2.2.1). 

Enigmail does not work with Thunderbird 78 or newer. If you want to continue using Enigmail, you'll have to stick to Thunderbird 68, or use Postbox or Interlink Mail & News.