Rated 5 out of 5 stars

It was a great plugin...
Not working with v68 but it's not the author fault.
Mozilla Team stripped a lot of code both from Firefox and Thunderbird.
This extension need to be almost written from scratch, I doubt that Author have the time and desire to do so.
Maybe donations and making encouragements will help, instead of scu**** that give only a star as a "token of appreciation".
Otherwise, there are other mail clients, not free, that can have a separate html signature for each email account (I will not lit them here, Google and read reviews, tests) .
Thanks Dev, have a great life.