I have some notes from an earlier thread and references. These refer to reverting to ff 52.0.2, which I couldn't find in the files, so used ff 51.0.1:
So the fix for the moment for me was to rollback to the last version before 55.0.x
which is 52.0.2....armhf.deb
First! make a backup of your /home/(username)/.mozilla/firefox directory. This holds
your profile, bookmarks, history, etc.
I assume you all know how to make a backup of a directory and even a hidden directory
(from either the gui or cli) if not Google is your Friend
Now this is what I did to get back a working version of Firefox, (this is utilizing
both gui and cli):
Launch Filezilla and go to ftp://ports.ubuntu.com (anonymous login), in the Remote
site: window type in /ubuntu-ports/pool/main/f/firefox if you don't have Filezilla
installed you can install it or use ftp from the CLI(terminal window).
Next scroll down and find firefox_52.0.2+build1-0ubuntu0.12.04.1_armhf.deb,(scroll
to the bottom) click and drag the file over your home directory
(If you use ftp from the command line I am assuming that you know how to make your
way to the directory and file that I specified above and the commands to download
Open a terminal window and go to the directory that you use to download the file
Now we have to remove the existing bad version of Firefox before we can install
the package we downloaded..
sudo apt-get purge firefox
From the download directory where the firefox.xxxx.deb file is stored run the following
sudo dpkg -i firefox_52.0.2+build1-0ubuntu0.12.04.1_armhf.deb
After the dpkg was finished with the installation I launch Firefox from the command line.
firefox & while it was launching it complained about the language pack addons not being
compatible..... just ignore these messages, they are just warnings. Firefox should launch correctly
and open with the two default Ubuntu tabs.
Close down Firefox and now the icon for Firefox should have been installed on your
Menu bar. Click on it to open Firefox again, but this time it should open with your
profile so your bookmarks and preferences should still be okay. (For me this was the case.)
After its completed, you need to 'hold' that version of ff so the update doesn'r immediately overwrite.