Effectively 01. September 2024, Microsoft removes the options to do license assignment through the Microsoft Entra ID and the Microsoft Azure portals.
From this date, administrators must instead use the Microsoft 365 Admin Center to manage license assignments for users and groups.
Note:
This change is limited to the graphical user interface, and access to do license assignment using API and PowerShell is, for now, unaffected.

References:
- Assign or remove licenses
https://learn.microsoft.com/en-us/entra/fundamentals/license-users-groups
- Assign or unassign licenses for users in the Microsoft 365 admin center
https://learn.microsoft.com/en-us/microsoft-365/admin/manage/assign-licenses-to-users?view=o365-worldwide
- Assign licenses to users by group membership using the Microsoft 365 admin center
https://learn.microsoft.com/en-us/entra/identity/users/licensing-admin-center