I just tried with 6.5.0 beta1 and test.zip, and plugins are deployed:
-- Installing: /tmp/test-install/bin/apptest
...
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_messages.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_local.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_server.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_debugger.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_inspector.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_native.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_nativedebugger.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_preview.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_profiler.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_quickprofiler.so
-- Installing: /tmp/test-install/plugins/qmltooling/libqmldbg_tcp.so
-- Installing: /tmp/test-install/plugins/networkinformation/libqglib.so
-- Installing: /tmp/test-install/plugins/networkinformation/libqnetworkmanager.so
-- Installing: /tmp/test-install/plugins/tls/libqopensslbackend.so
-- Installing: /tmp/test-install/plugins/egldeviceintegrations/libqeglfs-emu-integration.so
-- Installing: /tmp/test-install/plugins/egldeviceintegrations/libqeglfs-kms-egldevice-integration.so
-- Installing: /tmp/test-install/plugins/egldeviceintegrations/libqeglfs-x11-integration.so
-- Installing: /tmp/test-install/plugins/imageformats/libqgif.so
-- Installing: /tmp/test-install/plugins/imageformats/libqico.so
-- Installing: /tmp/test-install/plugins/imageformats/libqjpeg.so
-- Installing: /tmp/test-install/plugins/iconengines/libqsvgicon.so
-- Installing: /tmp/test-install/plugins/imageformats/libqsvg.so
-- Installing: /tmp/test-install/plugins/xcbglintegrations/libqxcb-egl-integration.so
-- Installing: /tmp/test-install/plugins/xcbglintegrations/libqxcb-glx-integration.so
-- Installing: /tmp/test-install/plugins/platforms/libqxcb.so
...
Can you create an install trace with cmake --trace-expand --trace-redirect=cmake_install.cmake.trace -Pcmake_install.cmake please?