Hi
I don’t know off the top of my head if @gmc has included our patch which removes 480p/576p modes.
Instructions for installing Kodi v18 builds can be found here: [TESTING] Kodi 18 (Leia) builds for Vero 2 & 4K
Obviously the usual warnings apply, as they are experimental. If you want to downgrade to Kodi v17, you will need to reinstall OSMC.
Sam