by Jonathan Cutting (Developer) on Dec. 17, 2020 · link permanent

The Thunderbird team have done sterling work in keeping Thunderbird up to date with Firefox, but it has meant a significant re-write of the add-on last year, and a full rewrite of every component in the add-on this year - almost no code from the original can be salvaged. That work is in progress, and we would just ask you to bear with us (note that even now some of the underlying APIs we need to recreate all the existing features are not readily available).

Thanks, Jon and the Opacus team.