X11 keyboard detection bitrot on Linux?

[Joerg-Cyril.Hoehle at t-systems.com]

Hi,

Perhaps there's some bitrot that affects the handling of alt/altGr
keys on Linux?

Using WINEDEBUG=+keyboard on Macos yields exepected results. The 3rd
and 4th characters (|\ etc.) below show what's obtained when pressing
the alt key:
trace:key:X11DRV_KEYBOARD_DetectLayout mismatch for keycode 34, got 7/|\
trace:key:X11DRV_KEYBOARD_DetectLayout mismatch for keycode 36, got 8({
trace:key:X11DRV_KEYBOARD_DetectLayout mismatch for keycode 58, got <>??
trace:key:X11DRV_KEYBOARD_DetectLayout mismatch for keycode 73, got ,,..

On Linux instead:
warn:keyboard:X11DRV_KEYBOARD_DetectLayout 7 keysyms per keycode not supported, set to 4
trace:key:X11DRV_KEYBOARD_DetectLayout mismatch for keycode 16, got 7/7/
trace:key:X11DRV_KEYBOARD_DetectLayout mismatch for keycode 17, got 8(8(

None of the {[]}\ keys reached via AltGr-7/8/9/0 on the German
keyboard is printed by the keyboard detection code.  This causes
warnings for all keyboards (not printed by default) because none matches,
which presumably was not the case back when that code was written.
What has changed?

Regards,
 Jörg Höhle