SUMMARY
When using the Neo2 keyboard layout (setxkbmap de neo, see https://neo-layout.org/ for a visual reference if you attempt to reproduce this), Konsole seems to assume that some unspecified modifier is pressed all the time, causing it to emit incorrect CSI sequences for keys.


STEPS TO REPRODUCE
1. Start konsole
2. setxkbmap de neo
3. Press any arrow key

OBSERVED RESULT
Arrow keys are mapped to their letters (Up -> A, Down -> B, …).

EXPECTED RESULT
Arrow keys navigate the shell history or input buffer.


SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Debian/testing
(available in About System)
KDE Plasma Version: 5.26.0
KDE Frameworks Version: 5.98.0
Qt Version:  5.15.6
Kernel Version: 6.0.0-2-amd64 (64-bit)
Graphics Platform: X11

ADDITIONAL INFORMATION
This can be tracked down to the aforementioned modifier situation by looking into Edit Current Profile -> Keyboard -> Default (XFree 4) -> Edit… and using the input field for testing. The rules which match differ based on which keyboard layout is used:

Layout   Rule                                     Escape Sequence
de neo   Up-Shift+Ansi+AnyModifier                \E[1;1A
us       Up-Shift+Ansi-AppCursorKeys-AnyModifier  \E[A

This makes me believe that something in konsole, or its dependencies, assumes that there's some modifier continuously pressed while using the neo2 layout.

As this happens even right after switching layouts, I presume that this is no lingering state.

I also suspect that this may not affect just konsole; I also noticed that some other applications shortcuts have stopped working correctly (e.g. the password prompt of kontact/kmail does not react to the Enter key anymore, I have to click Ok explicitly) and it may be related. 

If this is true, I'd like to know where to file this and how to help to debug this further. Is this Qt? Is this some KDE library? How can I help?