Hello,
in the FAQ it says that you just have to activate the Firefox Sync via the settings. I have done this, but when I try to log in to the Firefox page, the login hangs.
When I try it on Firefox it works without problems. So what am I doing wrong?
I had a similar problem caused by some addon (I do not know which, though. Could be ClearURLs). Finally, I managed to log in to my Firefox account through private window mode (opening the settings from the private window). I have never encountered this type of error with a clean LibreWolf installation, though.