Salut @stephdl,
Just to keep you informed.
I am still working on the warning in the URL when accessing Discourse with Firefox or TOR.
There is no warning with Chrome.
If you login with 2 different browsers:
- With the first browser, enable “force https”. Refresh the page. The warning disappears but you’re no more able to login.
- On the second browser, disable “force https”. Go back to the first browser, you are able to login again.
It looks like it is related to the SSL configuration in zzz_discourse.conf for Apache.
I tried both .crt and .pem; same problem.
If you use nginx, there is no such warning in Firefox.
I will try to find out more info on SSL config for Apache and let you know.
Continue having a nice holiday in the canyon 
Michel-André