After an update of the ibus component from 1.5.28-3.1 to 1.5.29-1.1, the
German-specific keys (ä, ö, ü, ß) on the German keyboard stop working in the
MAME emulation framework.

The keys in other applications are not affected, but in MAME, they are
frequently used, and thus this update makes MAME unusable in large parts.

To my understanding, the keys are scanned for raw keycodes in MAME and then
mapped to the respective emulated system, so the ö key should actually deliver
"COLON", but as stated, does not do that anymore after the update but is
completely dead.

I was able to retain the key function by blocking the ibus component update in
yast/zypper. Everything else could be updated, as checked right now (kernel
6.6.6).

I am involved in the MAME development, but I'm not familiar with those core
functionalities. I may be able to pass information to the suitable devs.