Which folders do I need to backup on OSMC to maintain all Kodi settings?

I’m using a combination of borg backup and RClone to automate my backup of my home directory as well as /etc to my Google Drive.

Are there any other folders on OSMC that I need to backup to be able to restore all my previous Kodi settings, addons, etc?

All your customization’s of Kodi should be in .kodi so you should be good to go