Sorry, I’ve never tried to revert a package but I “think” synaptic can revert packages (system or otherwise) and shared it because I wanted to make sure it works on Linux mint. Maybe I should have clarified that’s more of a “best guess” on my part than something I’m sure of.
The risk of rolling it back is even if brave works fine with an older version, if a different piece of software was tested with the newer version and expects it you could end up with a situation where other pieces of software that depend on it either break or keep trying to force you to update.
If you have a system backup and all you’re risking is time then I’d say go for it, just wanted to bring up the potential risks and some other options as well.
In the case of Firefox profiles maybe I can actually provide some useful info this time.
“firefox -ProfileManager” brings up the GUI profile manager and “firefox -P [profile name]” boots a particular profile.
Anyway, good luck.