Hello,
I used KDE in the past and I used the Global Menu widget for moving the menubar of all applications to a panel instead of the respective window.
I moved to i3 a while back and everything was fine, but recently, after I updated my system, the menubar, which previously showed up normally inside of the respective widnows in i3, has vanished for most apps. What I found out was, that KDE has changed the behavior of this widget since I used it. Before, it had a special toggle in the settings, but now, it automatically turns on if you add the widget. I didn’t touch the settings when moving to i3, so it was definitely turned on when I last checked, but I tried removing all the Global Menu widgets. In KDE, the menubars now show up normally, but not under i3. I made libreoffice work by removing the package libreoffice-gtk3, but that’s far from a permanent solution and it obviously dosn’t solve this for other apps.
It is surprising how unusable programs are without the menubar.
Thanks a lot for your help,
GS
Poke…
Poke 2 …
I guess no one here has a solution 
…
Why not file a bug report over at KDE’s bugzilla: https://bugs.kde.org/
To be honest I don’t know if it’s a bug. It might be a weird combination of configs and installed packages, but I don’t know where to find more information about what can cause this. It’s probably worth trying.
Just an update to this, so I don’t keep it unsolved here.
TL;DR I used a script to remove the menubar without knowing it.
Today I learned why this happened. I started using this: https://github.com/RafaelBocquet/i3-hud-menu
What I realised was, that this not only enables a HUD like menu for i3, it also removes the original menubar. It reappears when the script is stopped.
Thanks for that update.