Mobile + Identifier First + Enterprise Connections

Has anyone implemented identifier first on an IOS app? We support multiple enterprise connections and are able to choose the connection at login time based on the email address. This seems to work out-of-the-box on web, but we haven’t found any way (other than building that ourselves and even then we’re not 100% sure). I see that Universal Login doesn’t support it yet. Is this something that there’s some other pathway to support? Do you have to prompt for email address, then start the authentication cycle with a connection specified?

Interested in approaches and war stories.