As detailed in this mail, Jesper currently maintains a patch(feature/remote-video-player) to play video files on his Windows machine smoothly:

So in the end I wrote a very simply windows app which listens for a
connection from KPA, and once the two are connected, KPA will tell the
windows app to play videos for it.

While I'm not currently willing to merge this workaround as-is to mainline KPhotoAlbum, parts of it can possibly be used to implement MPRIS support (T8230) and/or the video feature can be implemented on top of MPRIS.