There seems to be a lot of stages where a browser might try to connect securely, even if you use http://, or try to locate the server for a secure connect (and not rely on just the port) that is causing the problem. I know Firefox and Brave both fail to connect no matter what I do with the settings. MS Edge worked for me. Others have said Chrome works. Probably some other browsers work as well. Interestingly, for me, I first noticed the problem a few weeks ago, just after a FF update was installed.

 
Other that the site getting with the 21st Century and moving to https I don't think there is much for them to do to fix the issue. I'm not sure if they own the servers or have the site hosted by someone else, but if the latter then the hosting company's security policies probably are not going to change for them. Just try some other browsers to see what works for you.