I have updated OSMC Forums [HowTo] Spotify-Connect support via Raspotify (LibreSpot) to make clear it is a Raspberry solution since Raspotify is a LibreSpot wrapper for Raspberry Pi. There is no generic/native OSMC solution (yet).
I am not a developer but anyone who wants to try can talk here about creating an OSMC app: LibreSpot in the OSMC App Store.