Entra ID Free: what happens to already joined and Intune-enrolled PCs if I reset the MDM user scope to "None" after Intune licenses were removed?

I have a Microsoft 365 nonprofit tenant on the Microsoft Entra ID Free plan, with users on Business Basic. Previously I had higher-tier licenses (Business Premium) included in the nonprofit offer, which have now been removed.

With those licenses I joined 9 Windows PCs to Microsoft Entra ID, and they were automatically enrolled in Intune. Today, in the Entra device list they show MDM = Microsoft Intune, management = Microsoft Intune and compliant = No. Users without an Intune license can still sign in on the already-joined PCs.

A new PC cannot complete "Join this device to Microsoft Entra ID" with a new user who has no Intune license. In the sign-in log the authentication succeeds, the resource is "Microsoft Intune Enrollment" and no device registration event appears. In Entra, Mobility (MDM and WIP) shows the Intune app as enabled, with the link to reset the scopes to "None" (I have not clicked it).

I have already searched the Microsoft Learn documentation and Microsoft Q&A threads: I found that with the MDM scope set to "None" automatic enrollment is disabled for new joins, but I found no reference on what happens to devices that are already joined and enrolled, or to users without a license, when the scope is reset on an Entra ID Free tenant. If anyone can also point me to a reference in the official documentation that covers this case, I would really appreciate it.

Questions:

1. Is the still-active automatic enrollment the cause of the failed join? Is setting the scope to "None" the fix?
2. If I reset the scope, do the already-joined PCs stay joined to Entra? Can users, even without a license, keep signing in with the same credentials and local profiles, without data loss?
3. What happens to the existing Intune enrollment on those devices?
4. Without Entra ID Premium, how do I bring the non-compliant devices to an unmanaged state without re-joining them and without losing profiles? Is there a documented procedure?
5. Is the scope reset reversible on Entra ID Free?

Thanks in advance to anyone who can help.