> I could see that this is also an issue for scam apps.

I don't deny that it can be used to reduce scams, but I think there are far better ways to solve this that don't give authoritarian countries extra powers. Thing is, signing doesn't actually address the problem. It is a way to track the problem, not prevent the problem. Don't confuse the two.

  > Firefox for instance does not allow you to install unsigned extensions.

That's absolutely not true[0]. You need to sign the extension to publish it to their app store but you don't need it to install. Btw, the Playstore already does this too. Which I'm totally okay with!

[0] https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...

  For other people to use your extension, you need ***to package it and submit it to Mozilla*** for signing.