When you onboard your Windows device in Intune, the device is automatically associated with the user registering the device; this user is called Primary User.
Until now, it was not possible to change the primary user, unless unregistering and re registering the device using another user account.
Good news, changing the Primary User associated with a Windows device is now possible.
NOTE this option is only available for Intune managed devices; it is not yet possible to do such thing for co-managed devices (this is the roadmap)
To do so, logon to either your Azure portal (https://portal.azure.com/) and reach the Intune\Devices\All devices (or Azure AD devices) blade or Endpoint Management portal (https://devicemanagement.microsoft.com/) and reach the Devices\Windows\Windows devices blade
Then you can search for the device you want to change the primary user and then go to the device Properties blade to switch (or remove) the primary user
In addition of this new feature, a new RBAC permission has been created – Managed Devices\Set primary user – to allow you delegate the permission to change the primary user.
The permission has been already granted to Helpdesk Operator, School Administrator, and Endpoint Security Manager.