The reason I am posting this is that Mozilla started Firefox as a freedom-respecting project but later betrayed its principles by implementing a glorified backdoor known as add-on signing.
Mozilla implemented mandatory add-on signing in Firefox in the mid-2010s, As expected, it is excused with "protect the user". Sounds quite Google to me - they also use that protection excuse to lock down Android OS and make it less useable and more like iOS (context 1, context 2). Microsoft did the same with Windows (context).
I could explain why mandatory add-on signing that is a bad thing, but it is already thorougly explained here (digdeeper.club) and here (change.org).
Even if Mozilla promises to "never abuse this", a government could force Mozilla to remotely censor unwanted extensions, and besides, there was a certain 2019 accident.Notice the slippery slope? First it was just a warning, then disabling unsigned extensions by default but still letting you enable them; and finally removing the option to install the addons without Mozilla's approval completely. Firefox will also disable any unsigned addons you might already have.
Please don't make the same mistake that Mozilla made.