Hi @PAB
Thank you for reaching Microsoft Q&A forum!
I understand that you would like to purchase licenses in Microsoft Entra External tenant and assign it to users who existed in the External tenant.
The Microsoft Entra External tenant is in preview, features or capabilities that require a premium license are unavailable in external tenants.
Microsoft 365 Business Basic licenses are typically tied to the tenant where they were originally purchased, these licenses cannot be transferred directly from one tenant to another.
Adding, removing, and reprocessing licensing assignments is only available within the M365 Admin Center. Go to M365 Admin Center
Instead of assigning a license to a single user you can assign licenses to security groups and the users to the security group to assign licenses automatically.
In summary you can purchase and assign licenses in workforce tenant and tenant user. In Microsoft Entra External tenant feature is unavailable.
Reference: https://learn.microsoft.com/en-us/microsoft-365/admin/manage/assign-licenses-to-users?view=o365-worldwide
Hope this helps. Do let us know if you any further queries by responding in the comments section.
Thanks,
Akhilesh V.
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