@Alex, Thanks for posting in Q&A. If the non-compliant devices are not being used in Intune, there is no action that needs to be taken within Intune. However, it is important to have clear policies and procedures in place for managing devices to ensure the security of your organization's resources.
For example, you can configure Intune cleanup rules to automatically remove devices that appear to be inactive, stale, or unresponsive.
For the device that is not used, you can retire or unenroll it from Intune. For any device that will give to new user, you can wipe it.
Hope the above information can help.
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