There are limits to the number of devices that can be onboarded with your Azure account. The maximum number of devices per user can be set by Intune enrollment, Azure Active Directory (AD), or Azure AD registration. The maximum number of devices per user in Azure AD for Azure AD join is 50. However, the recommended number of devices to onboard when using the local script method is up to 10.
https://www.anoopcnair.com/maximum-number-of-devices-per-user-azure-ad-avd/