Comment # 1 on bug 1091816 from Wolfgang Bauer

Is this really specific to Konsole, or does it rather happen with *all*
applications?

Sounds like a keyboard layout with dead keys is used.

Did you change the keyboard layout in KDE's systemsettings5?

If not, it's rather not a KDE problem I suppose, although I'm not sure at the
moment how the systemwide keyboard settings are handled in Wayland. (for X11
they are in /etc/X11/xorg.conf.d/00-keyboard.conf, which is generated by the X
startup scripts if it doesn't exist, using a mapping table)