Unity In App Purchases (IAP) not supporting text mesh pro (TMPro)

I’ve recently thinking about add an in app purchase for removing ads and followed a tutorial to do so but it seems like the IAP button supports only normal ui not tmp ui

To answer your question. The specific no code integration supplied by unity is not written in a 3rd part UI framework no (edit: I forgot Unity bought it). It is written using their own UI framework.

Unity In App Purchases has nothing to do with the GUI the GUI calls into it. You can emulate what that button is doing without even having a button. As per the documentation