Mac OS Client - Broken for WVD

To add a workspace by using an email address you need to add a DNS record to your domain used for email, as described here: https://ucnme.wordpress.com/2020/04/22/azure-wvd-how-to-configure-email-discovery-to-subscribe-for-rds-feed/  and here in the official MS documentation: https://docs.microsoft.com/en-us/windows-server/remote/remote-desktop-services/rds-email-discovery 

Alternatively you can enter the feed url instead of the email address in the client: https://rdweb.wvd.microsoft.com/api/arm/feeddiscovery

or https://rdweb.wvd.microsoft.com/api/feeddiscovery/webfedddiscovery.aspx (for WVD classic)