that is my system :
Operating System: Garuda Linux
KDE Plasma Version: 6.2.0
KDE Frameworks Version: 6.6.0
Qt Version: 6.7.3
Kernel Version: 6.11.0-AMD-znver3 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800X3D 8-Core Processor
Memory: 62,7 GiB of RAM
Graphics Processor: AMD Radeon RX 6800
Manufacturer: Micro-Star International Co., Ltd.
Product Name: MS-7A32
System Version: 1.0
yes, the demo was in kate.
and thank you @meven very much.
The workaround works.
It’s no fun doing coding with no properly working copy-paste 