How can the maturity model be extended with a team health check?
Think of it the other way round. What is holding the team back in terms of gaining maturity? Why is some sort of "extension" needed to inspect and adapt and improve team health? Why aren"t the Scrum Events enough?
In order for the team to grow, you need a mature mentor who can adjust all work processes and then things will go better. This is my personal opinion.
Where can I find the maturity model?
Hi Spotify has some kind of Health Check for their Squads, this could be helpful. https://engineering.atspotify.com/2014/09/squad-health-check-model/