In Firefox, it works perfectly fine.
No matter, how I set up LibreWolf - it refuses to show the login part of the page, when trying to access a private instance.
Out of desperation, I enabled all tracking etc. possible, which I would find in the settings. Disabled HTTPS-only mode, HTTPS over DNS, etc. Nothing works.
Have you tried it to disable “enforce OCSP hard-fail” and “resist fingerprinting”? You could also try to disable uBlock origin for that site.