Ubuntu – Missing menu in Kate

I actually had this same problem not long ago. I have since fixed the problem. Unfortunately, what i did wasn't pretty. I created a new account and then deleted EVERYTHING from my home directory and moved everything from the new account to it. Meaning that I had to reconfigure everything. Of course, shortly after that I found a possible solution to the problem. The problem MAY be caused by a corrupted highlighting definition file. To easily test this try disabling highlighting and see if the issue goes away.

If that worked for you then you'll need to get another copy of your highlighting definitions which aren't borked. You say you can use other accounts just fine so try to just use the ~/.kde/share/apps/katepart folder from a working account in your account. Just delete yours and copy the other over to the same place in you profile.

Hope it helps and let me know.

Seems to be a bug. Check here (answers #10 and #16): https://bugs.launchpad.net/ubuntu/+source/dolphin/+bug/1509562

In short: installing package 'libqt5libqgtk2' before 16.04 and 'qt5-style-plugins' for 16.04 and later brings back MOST of the icons in KDE-Applications. For the few remaining ones, you have to fiddle around with the icon-settings in KDE-System-Settings.

HTH