Hi @Swivel1660
Thank you for posting this in Microsoft Q&A.
As I understand it, your question is whether it is possible to using Realm Discovery policies or just a Sign in with Entra ID button for both local accounts and Microsoft accounts in your SPA application.
Unfortunately, as of now In External tenants the Microsoft Entra ID Sign up option is unavailable because although customers can sign up for a local account using an email from another Microsoft Entra organization, Microsoft Entra federation isn't used to authenticate them.
Feel free to express your feedback regarding these on our feedback portal https://feedback.azure.com/d365community/forum/22920db1-ad25-ec11-b6e6-000d3a4f0789. All input shared in these forums undergoes monitoring and review by the Microsoft engineering teams responsible for developing Azure.
For your reference: https://learn.microsoft.com/en-us/entra/external-id/customers/how-to-user-flow-sign-up-sign-in-customers
Hope this helps. Do let us know if you any further queries.
Thanks,
Navya.
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