Depends on the pub. Where we play there is a gentlemen’s agreement that no one uses phones to help them answer questions

Sure, but that ruins the ability to just pop into a pub and play with people you don't know (let alone trust).

I have this business idea for a pub in a faraday cage that would make cheating impossible for pub trivia (added bonus: also removes any other reason for anyone to be on their phones!)

I agree but I think we shouldn’t limit this answer to pub trivia. What other aspect of human society and civil discourse did we lose because we never argue or discuss any more?

Well it certainly sucks in cases where someone "fact checks" you but they do so before a broader discussion has given them enough context to even know what to google or ask the bot.

It turns out the internet has created more things to argue about than it destroyed.