Thanks for pointing this out. I wasn't aware of this feature.

I enabled Firefox sync and lost all my history. It was a user error: I should have disabled configuration sync (clear history when you close the browser).

After this incident, I decided I had enough, so I uninstalled LibreWolf. I recovered my lost history from different instances, but I don't want to spend my time making this browser work.

LibreWolf is a decent browser with annoying default settings, which made me lose more time than I wanted to make it work.