I experienced a graphical issue and opened a topic on the KDE Discuss forum ( https://discuss.kde.org/t/what-is-going-on-with-dragon-player-whole-screen-is-white/29312 ) and at the end of it I discovered that "vlc-plugin-ffmpeg" is necessary to deal with the issue. It appears that installing Dragon Player doesn't pull this package which is necessary. Thank you for all you're doing.
Looks like Dragon Player will be switching to QtMultimedia: https://invent.kde.org/multimedia/dragon/-/commit/c951fff6635d0ac24a71469171a505a1d7878426