It'll need to be developed extraterritorially, otherwise they'd just pick up the people developing it. They'll ban the original website, so you'll have to get it through dodgy means, which means they can insert backdoors for you (unless you're able to verify the code and compile it for yourself).
Have you heard of the hush-hush over Chat Control, a recurring theme on this site? It's getting to the point that they could shoehorn that with age verification push.
Yes, but they have to fit it around the judgements of the different European courts, and they really can't do it, so they try to say 'Oh, this is totally voluntary' and then when realise that that won't work they decide to go after companies, etc.
They have some political power, but they don't have all of it and they are quite constrained.
There's a legal right to end-to-end encryption and there's nothing preventing you from making a system look like HTTPS.