As of uBlock Origin version 1.49.2, you can now install the extension for Mozilla Thunderbird (see release version). The extension page on Thunderbird Add-ons states that it works with Thunderbird version 91.0 and higher. I use uBlock Origin with Firefox and I also use Thunderbird as my desktop email client (see my article on using Thunderbird with DecSync). I installed uBlock Origin on Thunderbird and restored my settings from my set-up on Firefox. The installation and export worked perfectly, but the non-uBlock Origin filter lists that I have enabled did not update (I am not sure if that is a general issue, but not important in my case). Consider this a PSA for Thunderbird users. If you want an aesthetic Thunderbird set-up, see my short post on the Two Little Birds theme.