1. Hackers acquiring private keys and stealing an actual NFT (the token) and moving it into an account they control. Aside from the base-level cryptocurrency malware/phishing, this doesn't seem prevalent, and is really the only thing in this list I'd describe as actual theft.
2. Non-artist creates an NFT using someone else's art, without their knowledge or permission. This might be a copyright violation, depending on the terms set by the original artist when publishing their work. Maybe it's a derived work... is "this jpeg but as an NFT" art in and of itself? I don't think so, but what do I know. This seems like what you're referring to here.
3. Artist creates an NFT of a jpeg of their own art, and then either sells or keeps the NFT. Later, someone views the corresponding jpeg in their web browser, right-click -> save-as, now they have a digital print of art that they paid nothing for. I've seen NFT cryptobros sensationally refer to this as "right click fraud," but it really just sounds like crocodile tears. I mean, really. Everybody knows how browsers work. This is one of the many examples of why NFTs are utterly stupid, but this also seems like it would be a copyright violation, at best.
4. Various combinations of 2. and 3. Maybe you right-click "stole" some images from one NFT, and then mint your own NFT of bit-identical images on a different chain. Or maybe you modified the image encoding so that the images are pixel-identical but not bit-identical, and minted NFTs on the same chain. This is all still just "maybe a copyright violation" until you try to pass it off as something it isn't, and then it's "maybe fraud" as well.