What’s the catch? AFAIK, you can’t even do that on desktop without manual reactivating the add-on every restart.

Edit: “you should be aware that you can’t use it to install unsigned add-ons. Mozilla believes they are security risks” There it is. What’s even the point of this? If you have to sign it, might as well just publish it. I want to run my own plugins without a central authority. I’ll worry about my own security.