Switch to using GStreamer backend directly
QtMultimedia already uses GStreamer as its backend on Linux, but it's behaviour is quite strange at times in its attempt to be cross-platform. Namely it is hard to select the location as to where audio files are stored, and also to select sane defaults for users to switch between audio formats. There have also been occasional bugs observed with qtmultimedia where sometimes the audio would stream to a different file from what is being observed.
This can be helpful: https://gstreamer.freedesktop.org/bindings/qt.html