I spent all night on this and couldn’t find any answers that worked for me on google. I reinstalled the Unity Hub, reinstalled and even updated the editor as well as Visual Studio. The solution I found was to go into “Player Settings…” under the “Build Settings”
If you want to build with IL2CPP you can navigate to Unity 2020.3.22 or replace “2020.3.22” with your unity editor version and there is a download for IL2CPP
Thank you so much. I just spent an hour trying to find a way to add this module as unity hub wouldn’t allow me for whatever reason, and was just proving seriously tiresome. Without seeing this random post by a stranger I would probably never have managed to add it. Unity really need to just “keep it simple” when it comes to downloading additional modules etc.