possible to generate qr code using only bitcoin core? Bitcoin core qt generates a qr code. Can I do it with the json rpc or by some other means without using 3rd party libs? Right now, I'm using a 3rd party lib and it's working; just trying to tighten things up if possible (with licenses, dependencies and maintainability).

I'm not looking to reverse engineer C code to do it; that would be overkill for the benefit probably.
QR Code creation is a GUI only thing. You cannot create a QR code without using the GUI. The JSON-RPC interface only works for text based things and cannot trigger GUI actions.