I opened Krita today to discover that its menu bar (File, Edit, View...) is no longer showing, and proceeded to test other application to find that their menu bars does not show either. (I don't know if this is related to KWin, Plasma or something else, feel free to move this post.)

Applications where I can NOT show the menu bar any longer:

* Krita (both 4.4.0 from repo and 4.4.1 from latest appimage)
* Kwrite
* KSysGuard
* Konsole
* LibreOffice
* Atom
* Skype

Applications where I CAN still show menu bar:

* Intellij IDEA
* Firefox (pressing alt)
* Thunderbird

My work around so far has been to add the Plasma "Application Menu Bar" panel to one of my screens. That bar still shows the relevant menu items to applications in the first list. (Although I much prefer having the menu bar in each application window, so I haven't used that panel before.)

I suspect menu bars might not have been showing for two days now. I recently did a system update (using apt-get dist-upgrade) which made me unable to boot except in recovery mode, until I had: ran the update again, ran dpkg --configure -a and possibly some other things (I don't remember exact details).

Is there something I could try to make menu bars appear again in their windows?

Operating System: KDE neon 5.20
KDE Plasma Version: 5.20.2
KDE Frameworks Version: 5.75.0
Qt Version: 5.15.0
Kernel Version: 5.4.0-52-generic
OS Type: 64-bit
Processors: 16 × AMD Ryzen 7 3800X 8-Core Processor
Memory: 31,4 GiB of RAM
Graphics Processor: GeForce GTX 1080/PCIe/SSE2

Hi, ecen

I'm not sure if you are having the same problem that I had. I didn't try to run any programs, because my desktop had
a black bar on the top of my screen. It looks like an empty Gnome panel. Graphics card: GeForce GTX 1650 SUPER/PCIe/SSE2. In my case, the update for Nvidia driver to ver 450.80.02 created my problem.

If you can confirm that you have the same problem that I had, then I'll try to help you. The installation of new
drivers was challenging for me.

P.S. Actually, I did try to run Synaptic before replacing the drivers. I couldn't see the menu, which leads me to suspect that you are having the same problems
that I had. That black bar on top of the screen was covering it.

If you are still having problems, I'm not going to respond until the week-end. I just installed the latest kernel, and I had
sound problem mentioned by others. I think I fixed it now, but I want to make sure that the fix was not temporary.
I also want to see if the new kernel was needed with the Nvidia update.

P.S. again,
After restarting my machine, I see that a new Neon version has been released. 538 files to update.
One thing that I don't like about Neon is all the files that need to be updated with a minor version release.
This makes it hard to pinpoint the cause of a new problem. Maybe it will fix the latest problems that I see
posted here, but I won't be updating until I've made a Clonezilla backup of my system.

One big concern that I have is the update of libqt5core5a. Debian and Ubuntu has dropped support for QT4.
Debian claims that QT4 was too much to maintain. QT4 is needed for Peer Guardian, which is an absolute
must have program for my security, since the Linux world doesn't think that application firewall rules are
needed. I would like to thank Neon for not dropping QT4 support so far, but I would imagine that the day
will come, and my Plasma days will be over.

So to re-iterate, my problem is that the upper corner of several programs (Krita as an example) look like this:


but should look like this:


The menu bar is simply missing. Is this what you encountered?

In the update I did just before this started happening, I believe I updated to Nvidia driver 455. However, I have now tried removing the Nvidia driver and installing the Nouveau driver instead. This did not solve my problem. I have also installed the latest Neon update but this has not solved my problem either.

I've solved the problem.

I did some more research on this and learned that there used to be a plasma system setting that one could use to remedy this problem. However, this was changed in plasma 5.12 when, in order to make it easier to use global menus, a service would be started automatically whenever you activate some widget that lets you use global menus.

What solved it for me is an answer to that last post that says that you can disable the service that removes the menu bar from applications by going to System Settings -> Startup and Shutdown -> Background Services, and disable the "Application menus daemon". After a restart, all applications have their menus in their respective window again.

I'm not sure how I enabled this service in the first place (I only added a global menu bar as a workaround after the window menu bar had disappeared), but in any case this is fixed for me now

Glad to see that you have figured out your problem. Sorry to have wasted your
time playing with the Nvidia driver. Nvidia driver 455 was the solution that
I had in mind. I did not see it in the Ubuntu repositories, and I thought
that you might need help installing it. You obviously know a lot more than
I do.