It was a slow boiling. Today, there's no way to install an unsigned extension in Firefox at all, you now have to use Developer Edition binaries. For a company that says the end user should be the decider and hold the keys, Mozilla sure likes limiting our options. There was a way to place them in a directory for awhile, then a cli flag, then an about:config flag, then a few other inconvenient options that ultimately ended up being snuffed out.

Even Chrome has a flag you can flip and install an unpacked extension from file. Sending this stuff up to Mozilla for them to grace or relegating developers and corporate users to some unbranded or esoteric dev binary is offensive to the end user IMO. I mean, it's not even federation, just centralization. Sure you can host it on your webpage, but it needs to be signed by the mother ship either way.

Firefox removed "about:config" from Firefox on android as well. Maybe we'll get a cli flag escape hatch for a year when they do the same on desktop. Not trusting the end user in the name of security is not a Google-only play despite all the Moz Marketing.