When usig the hierarchical kicker start menu with sub menus, the menu can be navigated only in the first level using the keyboard (e.g., keyboard cursor arrow keys). Entering into a sublevel and choosing a sublevel item is not possible.

STEPS TO REPRODUCE
1. Boot Plasma with Wayland. Use the traditional Kicker Start Menu with cascading/submenus.
2. Open menu with Alt+F1 or whatever shortcut you have.
3. Choose any item, for example "Power / Session"
4. Try to select one of the options, such as "Shut Down" by using the keyboard navigation keys.

OBSERVED RESULT
The user is forced to use the mouse pointer device to select any item in any sub-menus

EXPECTED RESULT
The user should be able to select any menu item in any category by using regular keyboard navigation keys and activating any of these menu items by using the Enter key.

This is the case in X11, where the start menu behaves as expected.

SYSTEM INFORMATION
Operating System: Slackware 15.0
KDE Plasma Version: 5.23.4
KDE Frameworks Version: 5.89.0
Qt Version: 5.15.3
Kernel Version: 5.15.11 (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i7-8550U CPU @ 1.80GHz
Memory: 15,5 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 620

ADDITIONAL INFORMATION
As I said, the submenus behave normally under X11.