はっはーん、Qt5だと実行中に
Warning: QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-uaa' ((null):0, (null))
Warning: Warning: "No decoder available for type 'audio/x-wav'." ((null):0, (null))
Warning: Error: "Your GStreamer installation is missing a plug-in." ((null):0, (null))
となるところがQt6だとうまくケアできずに落ちてるのかにゃー?(根拠なし)