SOC CMM
https://soc-cmm.com/
NCSC's guide to meeting Objective C of NIS. Very helpful structure as to what 'good' looks like.
https://www.ncsc.gov.uk/collection/caf/cyber-assessment-framework/caf-objective-c-detecting-cyber-security-events
My questions to assess the maturity of an enterprise SOC. Click to pop out to a spreadsheet.