Authenticating with Entra External ID

[edalatpour]

I got authenticated sync to work using Microsoft Accounts. But I want to offer Google and Apple signin without a ton of additional work. It seems like porting my auth pipeline from MSA to Entra External ID (the successor to Azure AD B2C) is the easiest way to do this. But when I try to configure my identity providers in the external tenant, I can't add Microsoft as a provider. Has anyone tried this and/or gotten it to work?