Rated 5 out of 5 stars

by MangoShark on April 10, 2025 ·

Github explains that the add-on follows ESR channel which is still on 128 at this time. I wanted more/newer and found the intermediate (non-official) version for 136. Then I manually installed the unsupported xpi which brought it back to life in 137.0.1. So far it works.
Checkout https://github.com/rsjtdrjgfuzkfg/thunderbird-birthdaycalendar to assess the risks. I'll probably try to build myself next.
Otherwise 5*. Not fair to rate the add-on against newer version compatibility. Thumbs up to the author.