I actually think if you had all the nostr clients agree to shadowban anyone who mentions Bitcoin or zaps, directly or indirectly, in their posts, 'memes', slogans, bio, pfp etc etc.. For a period of like 3 years. That might be nostr's best shot :)
I don't see the UK government actually banning twitterX, but it is a good opportunity to tell people to get a 'just in case' nostr account.
Tbh telling people to join nostr will involve a caveat ("it's not really ready yet, it's most people talking about the price of Bitcoin").