kinda... (excepting the code tags for output pastes;D)
but I was not very clear in the steps, pushing you back towards Pjotr's site to help get FireJail installed by developer provided .deb (he recommends LTS version, safe bet for sure. I went for latest version locally to get past some issues I was having with symlinked directories)
you've reinstalled the old version from repos again2. sudo apt install firejail-profiles
The following NEW packages will be installed:
Do you want to continue? [Y/n] y
Get:1 http://archive.ubuntu.com/ubuntu bionic/universe i386 firejail i386 0.9.52-2 [258 kB]
Get:2 http://archive.ubuntu.com/ubuntu bionic/universe i386 firejail-profiles all 0.9.52-2 [34.8 kB]
so lets get you using the current version, 0.9.58.2 which I recommend (but considered a departure from norm by many, I do tend to go 'bleeding edge' release on packages I trust). Also note, the LTS version brings stability for business minded level of ops, current is recommended by dev for any who's Linux repos contain older versions.
So you have some options, and any one of which may help with the annoying behavior it seems FF has with repo version. Also see trytip's most recent response, this may also help clean up the firejail firefox profile you have and get what you have installed working properly.
Otherwise, to proceed, check this page:
Looking at that, the Decision you need to make is do you want most Current (release) version or LTS (LongTermSupport) version. Click the appropriate link and download the firejail and firetools packages from sourceforge as linked to in the developers notes on the above wordpress link posted.
LTS version or Current version and for Firetools
Note, if you install .deb it will be on you to keep it up to date as package manager won't update it until repos have a more current version. choices are current: 0.9.58.2_1 or LTS: 0.9.56
another note- installing the .deb(s) will integrate them into system package managers, namely synaptic and apt so uninstall and checking for updates will happen as expected, just you wont get updates until repos have a more current version.
anyway, once you have downloaded both the firejail and firetools deb's just double-click them, firejail first, and let gdebi-gtk check dependencies and install it for you. When it is done it confusingly reports "Same version already installed" on a blue bar at top, ignore this- it is saying it's installed is all (took me a moment or three to sort that out the first time:D). Do the same for firetools.
you could also install via PPA (also not a popular option with many, but in this case I consider it valid, especially seeing the PPA version is very recent 0.9.58-1 The nice thing about PPA installs is, once you establish trust in the PPA manager (he's got good launchpad karma:) and add them to sources in Update manager, the package will be kept up-to-date with Update manager, like everything else on LM from the repos, including ignoring the old version in repos and offering PPA updates mixed in with all other updates for your system. Always nice, imo, and no need to check dev site for new news and packages as would be required for straight .deb install..
PPA is here:
to add the PPA, in terminal paste and hit enter this command:
sudo add-apt-repository ppa:deki/firejail && apt update
then get firetools from sourceforge (is what I'd do, versus install old from repos again) and doubletap that deb
kinda wordy above (and sry if/for repeat myself, its an injury based character flaw;) anything unsure of please do continue to ask- it certainly wont offend or annoy me (I like this sorts of stuff
minor edit to clarify current version as released/sourceforge, not git/dev