I'd like to record a fix, of sorts, for a missing menu bar in Frescobaldi under a rather specific combination of circumstances. It might help someone. Possibly future-me!
I run Frescobaldi on an Ubuntu 22.04 system, with an Apple-Mac-OS-X- like KDE theme that puts the menus of the currently-focussed application at the top of the screen. Following a recent upgrade to KDE Plasma 6, the menus in Frescobaldi completely disappeared. You can force the menu bar to appear at the top of the application window for all apps. To do this, go to System Settings -> Session -> Background services and uncheck "Application menus daemon" It might be necessary to restart your session for this to take effect. It might be possible to create a specific exception for Frescobaldi, using the KWin rule editor, accessed by right-clicking on the title bar of the Frescobaldi window and selecting More Actions. Unfortunately I've been unable to find a specific combination of settings that work.
