Jellyfin Project Leadership Changes
forum.jellyfin.org/t-project-leadership-changesReplying to @A_norny_mousse@piefed.zip
So to answer your question: OpenSubsonic is only for music, and Jellyfin does much more than music. Adopting OpenSubsonic would mean maintaining two APIs, which doesn’t make a lot of sense.
Meanwhile Navidrome is adding Jellyfin API compatibility to get access to more clients :P