autodiscover in outlook app?

Question

Hello,

I'm migrating one of our customers to Azure, which involves an exchange migration from on prem to exchange online, but i'm running in to a problem connecting the outlook app (for both iOS and android) to the on prem environment.
We need to assign some licenses to users including one for exchange online to start migrating the mail in delta's, but as soon as the app finds the exchange online mailbox that is then created it completely ignores the actual autodiscover records, and will not connect to on prem.

As the phones will be migrated to intune before the exchange environment is migrated, i need some way to have the app connect to the on-prem in the meantime, any suggestions?

i've set up an app config policy in intune, which should point it straight to our on prem, which doesn't seem to work at all?
com.microsoft.outlook.EmailProfile.EmailAccountName
{{username}}
com.microsoft.outlook.EmailProfile.EmailAddress
{{mail}}
com.microsoft.outlook.EmailProfile.EmailUPN
{{userprincipalname}}
com.microsoft.outlook.EmailProfile.ServerHostName
mail.server.here

on windows you can use some autodiscover registry keys to influence this, which works fine, but obviously i don't have thoes on the apps, is there a way to force the connection? or can MS make an outlook app that uses autodiscover like it was ment to be?