This works on links and buttons in chrome. In firefox just on links. In both it doesn't work for other html elements.

I was going to disagree with you, but… huh. It doesn’t work on buttons. Thought it did. Selection is set, but focus isn’t. Further workaround: Shift+Tab.

This feels like it may be a bug, but at the very least it’s not a recent regression—I tested Firefox 44 and it shows the same behaviour. (44.0 is the oldest version I can run now, apparently. I tried 4.0 first, the first version with linux-x86_64 builds, which I have run successfully in the past, I think even in the last year, but now all versions before 44.0 are crashing on startup.)