Also the whole AI is “fair use” battle is not finished. AI companies like to pretend like it is but big part of “fair use” is that it doesn’t compete with the initial work… it’s hard to make a strong case there.

In either case "Fair use" is a thing very limited to USA and does not apply outside it. There may be similar things in other jurisdictions, but it cannot be assumed the same reasoning and rules apply.

Right, seems I can prevent AI training by marking a work here in Germany (via UrgH § 44b Abs. 3). That would be perhaps something to add to (a variant of) the GPL.

Doesn't prevent training in the US and use of the trained AI and material it produces here, I guess.

Then I have to start a civil law-suit and prove that the produced work is similar enough to the the original work. That was the step that failed in the Hellwig (Linux) vs. VMWare lawsuit.