But aside from re-minting it with alterations, you can mint the exact same digital artwork on different NFT platforms, so how do we know which platform is “right”?
The right one is the one the original author of the artwork released it on. The thing about NFTs is the connection between digital items and their authors.
If you're like most art collectors you'd follow the author anyway. You'd buy one because you're a fan of the author and enter their nft sales funnel.
How would this work?