I don't have any bitcoin wallets that haven't already been mentioned, and I'd like to know if it's possible to create a bitcoin-only wallet that doesn't require a desktop APP, works offline
I don't get exactly what you mean by this. Are you talking about a Bitcoin wallet that doesn't need to install on your desktop that works offline?
If yes, then a paper wallet is I think what you looking for because most Bitcoin wallet is software that you need to install on your desktop before you can able to use them.
Unless you talking about apps from the Microsoft store? If I'm right then you can use Electrum or Armory(with Bitcoin core installed) or Bitcoin core they do all will work without internet.