Hi @Andy ,
Thanks for reaching out,
As per my knowledge Microsoft Graph API will not be available for SharePoint on-premises/Server. MS Graph is Microsoft's API for their online services, so it wouldn't work on SharePoint OnPrem. Microsoft graph is part of Azure infrastructure and does not know anything about your local environment. To use Graph API you need to register an App in Azure AD. With an on-premises environment you can't perform this step since you are not connected to Azure AD in any way.
Hope this helps.
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