Safari forcing HTTPS for some HTTP only sites - SOLVED

If, in Safari, a http:// site is getting automatically redirected to https:// and you get an error it cannot open the page, it's due to HSTS. You cannot prevent that from happening with the regular Safari or by deleting the ~/Library/Cookies/HSTS.plist file. Just doesn't work.

EXCEPT if you download the Safari Technology Preview version where you can delete the HSTS Policy cookie for said site. And then it works! Your 'normal' Safari version will pick this up too, in case you don't want to continue using the preview version.

Was driving me crazy.

Note: Chrome and Firefox are not affected by this behavior.