I truly don’t know either way, but it would be laughable of them if the only thing that blocks unregistered users from loading more content is a pop-up. I’ve gotten through forced pop-ups with uBlock’s block element tool in the past.

I’d imagine it’s far more difficult (and possibly illegal) to forcibly gain access to a website that denies access until you log in or register. Maybe there could be an extension that creates throwaway accounts for you to use, but I’m not aware of any myself.

I wonder if it’s possible to register a VOIP number for free and use it for Facebook. I haven’t tried it myself.