Hi, Denise.
There are a few Linux users here. I'll message Pete! and see if he has any suggestions. If note, you could try Scot's Newsletter forum which has a large Linux user base, although I searched the forum and the most recent Linux Mint thread there is about the update to version 20.2. Pete! is a member there as well.
It would be helpful if you would reply with examples of any issues you've run into with Firefox, including which version update you're using.