@milo last, Thanks for posting in Q&A. Agree with S.Sengupta, we can deploy Feature update policy to the devices' or users' group you want to upgrade the devices to windows 11.
https://learn.microsoft.com/en-us/mem/intune/protect/windows-10-feature-updates
At the same time, please also configure windows update ring policy with Feature update deferral period (days) to 0 to ensure your feature updates aren't delayed.
For Microsoft 365 E3 license, it supports Windows Update for Business deployment service: But the devices need to be enrolled into Intune MDM and be Hybrid AD joined or Microsoft Entra joined. Here are other requirements, we can check it under "Prerequisites" part in the above link.
Hope the above information can help.
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