EDIT Using Unity 2019.4.13f1 seemed to do the trick. Unity has changed something in WebGL from 2020.1.
I tried the WebMonetization asset for Unity, but I am unable to make it work. I keep getting unityInstance not defined when monetization starts. I submitted an issue about it, but I appreciate any help if anyone might know what the issue is.
I tried it on Unity 2020.1.11f1