I wouldn't expect KODI/OSMC to provide an unofficial YT client. However, the "app" availability issue is a big one for devices like this if they are to compete with spyware-ridden Android TV boxes on one hand and Linux HTPCs on the other hand. The Android TV boxes are cheap and support all streaming platforms. The Linux HTPCs are free (as in freedom), typically far more powerful (can double as consoles/emulators) and don't restrict the user in any way.