There are no constraints from the Azure side of things. Just make sure that your VM meets the deployments requirements. You can find more information about deploying Office LTSC 2021 at these locations:
https://www.microsoft.com/en-us/microsoft-365/microsoft-365-and-office-resources#areaheading-oce1c3
https://learn.microsoft.com/en-us/deployoffice/ltsc2021/overview#overview-of-office-ltsc-2021
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