I'm experiencing the exact same issues with the 71.0.3770.148 version. I'm on Ubuntu 20.04. The actual problem is that the right click works, but the menus are not displayed. Not a single menu.
Should you click on a folder of the bookmark bar, you will notice that the bookmarks are not shown, but if you left-click randomly on any place a bookmark should be, the bookmark will actually work.
In any case, the UI is unusable this way.
Please fix this. Is an awful bug!