How to update the proxyAddresses of a Cloud-only Entra ID user

I currently have a client with an Entra ID user (not migrated from on-premises) that is cloud-based, but has proxyAddresses values assigned.

Now, I want to update the proxyAddresses through the Graph Explorer and have used this link as a guide: https://learn.microsoft.com/en-us/answers/questions/2280046/entra-connect-sync-blocking-user-creation-due-to-h.

Now this guide is suggesting you can use the BETA model and this URL format...

• https://graph.microsoft.com/beta/users/%USERGUID%

It states you can use that URL to do both 'GET' and 'PATCH' queries - the PATCH query being the one that will change the settings. You have to put forth a body for the proxyAddresses property in the PATCH query, which represents all of the addresses you want the user to utilise as proxy addresses.

Now the GET query works...

The PATCH query does not...

Screenshot provided:

Now, regarding the error message, I have applied ALL possible permissions in the 'Modify Permissions' tab. It is still erroring,

Now I cannot use Exchange Online PowerShell, as the user does not have a mailbox!

Aside from potentially using a license for Exchange Online or provisioning a mailbox for the user, and making the necessary changes, would the only other option be to delete/recreate the user?