Using mobile test websites on Discourse fails for some reason

I’m trying to see what my new forum looks like on mobile devices, but to my surprise, on every tool there is such a mistake: refused to connect

Isn’t that strange?

I checked on websites like this:

How did you install? Can you share the domain name? Does it work for you? Where is it hosted?

I think the “issue” is only that we do not permit to load cross-origin framing