When I try to visit certain sites and force http (for good reasons that do not need to be discussed here), Safari (macOS) forces the URL to use https - and since the site currently has no https support, I can't visit the site.
There are many answers that suggest that this is related to HSTS but this does not apply in my case:
The site in question is not listed in Safari's Privacy under WebSite Data nor does it appear in the HSTS.plist file. So, there is some other cause that forces Safari to use https, and I suspect it's from the fact that Safari has previously seen me visiting the site with https and now assumes I always want to do that.
Note that when I load the URL with wget, then I get the http version just fine. That should prove that it's Safari's behavior, not the web site's.
So, beside the HSTS settings what other settings might there be that force https in Safari on macOS?