Hi @FX , as of now, Azure Virtual Desktop (AVD) does not support Azure AD B2B (external users) for SSO. I unfortunately cannot speak on the future of this product. However, Microsoft is constantly working on improving its services and adding new features, so it is possible that this feature may be added in the future.
In the meantime, you can consider using other solutions such as Remote Desktop Services (RDS) or third-party solutions that support external user access.
If you'd like you can create a feature request here.
Please let me know if you have any questions and I can help you further.
If this answer helps you please mark "Accept Answer" so other users can reference it.
Thank you,
James