SUMMARY

On X, when having a top bar, Krunner opens under the top bar and blends with it visually (by being on top of the panel shadow and having no top border/shadow). On Wayland, it takes "under" a little bit to literally and openes under the panel on the z axis, meaning behind the panel, so you can't see what you're typing.

STEPS TO REPRODUCE
1. Log in to a Wayland session
2. Create a panel on the top of the screeb if you not already have one
3. Open KRunner (alt+space)

OBSERVED RESULT

KRunner opens behind the panel, so you can't see what you type.

EXPECTED RESULT

KRunner should be under the panel (on the x axis) like when using X.org. It should blend with the panel by having no top border but being above the panel shadow.

Linux/KDE Plasma: KDE Neon 5.18
(available in About System)
KDE Plasma Version: 5.18.0
KDE Frameworks Version: 5.67.0
Qt Version: 5.13.2

ADDITIONAL INFORMATION

This bug also occurs with Latte panels.