Hmm, my forum is a subdomain of my root domain, so I added the root domain as you suggested and got this error:
Uncaught DOMException: Failed to read a named property 'document' from 'Window': Blocked a frame with origin
Now I’m trying to do the postMessage thing but failing. I think I need to better understand how Discourse javascript works, I think I assume it works like other sites and maybe it doesn’t, or maybe it’s just me not knowing how to do javascript that well, especially for cross-origin stuff lol.
Thank you for taking a look at this!