Thanks for your attention to security! I will look forward to checking out the beta site.
Over two months later, I am still receiving exactly the same error as described in my OP. The certificate SHA-256 fingerprint is the same. Apparently, nothing changed.
I was waiting for this to be fixed; and then... I hadn’t tried it in awhile. It occurred to me that I should give it a spin, and test to make sure that the new forum software will be functionally usable with Javascript disabled.
But I still can’t even get in without blindly clicking through the very same warnings as I lecture newbies to never, ever, ever click through. How are people testing this? I can’t be the only one hitting this problem. Are people with similar browsers just clicking through the warnings?
...as I was saying. So, what are all these people doing? Clicking through the scary warning which is scary for a reason, or just not testing? Is the new software being substantially tested only by people who happen to use the same browser as the Slickage devs? For the record, my browser (Tor Browser) is essentially Firefox (currently 52 ESR) with some anonymity stuff bolted on. Firefox is a browser with significant market share.