Chrome doesn't require extensions to be signed? Or hasn't revoked the signature?
If Mozilla has unbroken the Developer edition, and it's available to everyone, great! Firefox is almost back to the functionality it had in 2016!
In any case, no, I'm not on a corporate firewall, you were kind of jumping to (oddly specific) conclusions there. And firewalls don't work like that.
I think the unbranded version doesn't update. Or used to not update. But that's not developer.