SUMMARY

If I try to copy some text from Scintilla widget and paste it into a KDE app, then nothing is pasted. Though, pasting into XWayland or GTK apps works fine.

The bug is reproducible both with Geany 1.38 ( https://github.com/geany/geany/issues/3320 ) and SciTE 5.3.1.

See also: https://sourceforge.net/p/scintilla/bugs/2361/. Quoting a Scintilla maintainer,

> Copying the path with the File | Copy Path command does copy to Kate. That is using the simpler gtk_clipboard_set_text API instead of gtk_clipboard_set_with_data which is called in Scintilla to allow multiple formats and asynchronous access. Its likely that the current KDE implementation on Wayland has a problem with this API or its use. Since it works with GTK applications on Debian + Wayland and also with KDE applications on Ubuntu + Wayland, I'd hope that it gets fixed with updates to KDE's Wayland support.

STEPS TO REPRODUCE
1. Open Plasma Wayland session
2. Open a Scintilla-based editor (SciTE or Geany)
3. Enter some text and copy it to the clipboard
4. Paste into a KDE app (e.g. Kate)

OBSERVED RESULT
No text is pasted.

EXPECTED RESULT
Copied test must be pasted into the KDE app.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 5.26.0
KDE Frameworks Version: 5.98.0
Qt Version: 5.15.6