Can a mobile app built with an MDM integration (Mobile Device Management solution i.e. Maas360, Airwatch, etc.), work on some other devices which are not enrolled in that MDM? Does this depend on which MDM in particular?
Yes, the app can work outside of MDM (unless you use a legacy app-wrapping techniques, not commonly implemented today, e.g. Knox v1 app signing service).
Important: while the app will work, the features that rely on MDM need to be coded in such a way so they gracefully fallback when MDM is not available (e.g. prompt for user input or disable features)