You could prove you had a link to a JPEG. Whether that link says you own it is up to interpretation.

Also I could upload that same image to another IPFS node and create a new link to that on the Blockchain.

Nfts were funny. Beyond the JPEG stupidity they were all just a solution that was so desperately searching for a problem to solve, and every time it turned out to be a massively more expensive way of doing things we can already do without nfts.