SUMMARY
I’ve discovered a bug using Plasma / Wayland / Libreoffice, where clicking simple dialog popups such as the font size or the font color result in failure to display the dialog. Or more correctly I can sometimes see the color chooser flash briefly in middle of screen. Therefore cannot choose color.
Under X11 there is no problem.

STEPS TO REPRODUCE
1.  Log into Plasma Wayland Sesssion
2.  Open LibreOffice, type some garbage, select the garbage
3. Go to pick the Font Color

OBSERVED RESULT
Color picker dialog may briefly flash in middle of screen, or simply not appear.

EXPECTED RESULT
Color Picker dialog appears at top fo screen and stays visible

SOFTWARE/OS VERSIONS
Operating System: EndeavourOS
KDE Plasma Version: 5.24.2
KDE Frameworks Version: 5.91.0
Qt Version: 5.15.3
Kernel Version: 5.16.12-zen1-1-zen (64-bit)
Graphics Platform: X11
Processors: 12 × Intel® Core™ i7-9750H CPU @ 2.60GHz
Memory: 31.2 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 1650/PCIe/SSE2

Version: 7.3.1.3 / LibreOffice Community
Build ID: 30(Build:3)
CPU threads: 12; OS: Linux 5.16; UI render: default; VCL: kf5 (cairo+xcb)
Locale: en-GB (en_NZ.UTF-8); UI: en-US
7.3.1-1
Calc: threaded

ADDITIONAL INFORMATION
Same thing happens with other drop-down menus like font size.