I have temporarily made it possible to connect using http:.
In the future, a 301 directive will forward an http: request to https:
I want Firefox 45 (and Chrome 49 and IE

to be able to connect, too. All other browsers listed in the report (in my prior posting on page 1) work fine on https: now.
The problem is in the configuration of ciphers on nginx. I don't think I have access to that, so I'll need to open a ticket with my upstream provider.