If a country like the UK decided to ban end-to-end encryption, how would they even enforce it? I understand that they could demand big companies like Apple stop providing such services to their customers and withdraw certain apps from the UK App Store. But what’s stopping someone from simply going online and downloading an app like Session? I mean, piracy is banned too, yet you can still download a torrent client and start pirating. What would a ban like this actually prohibit in the end?
You’d be surprised at how much an off-the-shelf firewall can see and categorize. A purpose built application that regulates/controls the physical network would have no issue with that type of traffic.