I'm affected of the "invisible" burger menu aswell. After click hovering over it shows there are the menu buttons below.
I didn't notice the problems with the bookmarkbar or context menus mentioned by gpothier.
Burger button stopped being displayed normal since FF56. Downloaded the FF56.01 tarball, same behaviour.
Xubuntu 14.04.5 LTS (4.4.0-97-lowlatency) Firefox 56.0+build6-0ubuntu0.14.04.2
I'm affected of the "invisible" burger menu aswell. After click hovering over it shows there are the menu buttons below.
I didn't notice the problems with the bookmarkbar or context menus mentioned by gpothier.
Burger button stopped being displayed normal since FF56. Downloaded the FF56.01 tarball, same behaviour.
Xubuntu 14.04.5 LTS (4.4.0- 97-lowlatency) 0ubuntu0. 14.04.2
Firefox 56.0+build6-