In the 22.04 version of Ubuntu/Kubuntu, Firefox was switched from a repository to a snap. I don’t know enough about the technical reasons for that, but it does mean that how Firefox is updated has changed. It also introduced a very annoying notification message that you’ve probably seen (and which is why you’re here:
Switching to a snap is fine, but forcing users to employ a different update method is a bit annoying. Even so, this just requires one line in a console to update Firefox now. You don’t, technically, have to close your Firefox browser to run this as the code will take care of that. Here’s the code:
sudo killall firefox && sudo snap refresh
To explain the code. The first part tells the OS to shut down all instances of Firefox (sudo killall firefox). After that, the two “&&” symbols tell the OS that there is a second command that follows the first. The second command tells the OS to refresh all your snaps (sudo snap refresh). When you run this line of code, you should see the snap downloaded and installed.
Also, the notification message likely won’t go away after running this. It should and I’m not sure why it doesn’t. But you can just click the “X” to make it go away since your snap of Firefox has, in fact, been updated.
(NOTE: I found a solution to this problem here. I put up this post because I like my solution better. It’s a single line of bash script and solves the problem.)