This seem to be previously reported as QTBUG-83783.

I believe QComposePlatformInputContextPlugin and QIbusPlatformInputContextPlugin should be linked by default given that compose/dead keys/CJK input support is expected to work out-of-the-box and QtGui already links to QtDBus and xkbcommon so those plugins don't add new deps.

That seem to happen due to DEFAULT_IF FALSE at https://github.com/qt/qtbase/blob/0a6647a1edd02c3c1f0c236dec1fd9ae873b9cff/src/plugins/platforminputcontexts/compose/CMakeLists.txt#L14 and https://github.com/qt/qtbase/blob/0a6647a1edd02c3c1f0c236dec1fd9ae873b9cff/src/plugins/platforminputcontexts/ibus/CMakeLists.txt#L11.

It should perhaps either being removed or have a condition to be linked when either xcb or wayland is in QT_QPA_PLATFORMS. GIven that both plugins get built only when QT_FEATURE_xkbcommon is enabled, just removing DEFAULT_IF FALSE should work just fine.