4chan’s position is that they aren’t doimg business in the UK, which is why they’re disregarding the UK regulator’s fines. The UK might be able to block them, but probably not get the US to enforce rulings against them.

In the same way, lemmy.today is doing business in the EU.

Very unlikely, in the eyes of the US court system. They have no EU physical presence, and aren’t advertising targeting EU people.