In Ubuntu 26.04 transmission and firefox seem to bei infected by the snap noiseware.
The Test of the system installs normally with snap in a Live DVD. Then you can login use the normal snap remove procedure and it works almost normally.
However transmission and firefox somehow depends on the unwanted snap. Tomorrow i'll try to install firefox from ppa, transmission does not work due to apparmor beeing configured for a buggy? snap version of transmission. I'll try to Look at it again and give Feedback. There hast to bei a way to use both Apps without snap
I have used Ubuntuzilla: Mozilla Software Installer for about 5 years without any problems. It is a repository not a PPA. It includes Firefox, Firefox ESR (you can run both they have their own profiles) Thunderbird and Seamonkey. I also use their Thunderbird. They do update a few days later than the official release.
Install your desired package, with one of the following commands:
Yes I couldn’t get the repository Thunderbird to run gmail it said it was insecure years ago but the Ubuntuzilla worked. I also like that you can run Firefox and Firefox ESR and they don’t share the same profile, both are separate. Now and then (years) you do have to update the authentication keys for the repository.