The package has been out of date for over a year. Version 2.30.5544.102 has been released upstream. Reproducible: Always
Starting with version 2.29.5374.102[1], the mozc GUI migrated from Qt5 to Qt6. Maybe someone with privileges could tag this bug on the Qt5-removal tracker. [1]: guesstimated off of these commits: https://github.com/google/mozc/issues/775