How to stop Safari on macOS from using https when I want http, when it's not in the HSTS listing
I believe I have figured it out:
The site is an .app domain, e.g. domain.app. And those sites are by definition https-only. See here.
So, it's still HSTS related, but not on an individual site but for the entire &quot;.app&quot; TLD. And for that reason I could not find the specific domain name listed in HSTS, not would deleting the HSTS.plist help.
Well, not sure if I should keep this question up. Maybe it helps others that run into this.
Background: It was my own site. I moved it, along with others, to a new server, and need to verify that they work with plain http. So I tested every site in http, and all but this one worked. So I assumed something wrong with the browsers.
And not only Safari but also Firefox and Chrome want to do https only.
Strangely, though, using other way to request the http site, such as the low level command wget, do not enforce the https requirement (they don't know about it, obviously), hence it misguided me into thinking the problem was a latent browser setting that I could fix.