It is possible to include a domain hint in the oAuth SSO settings. For the steps to configure oAuth click here. The regular oAuth flow is as follow:
In the normal flow the Federated domain check is done after the user fills in the UPN. In the configuration with domain hint, this is already preconfigured by the admin in Workspace. In this way the SSO reply url to will have the value of the federated domain included.
The domain hint option provides a hint about the tenant or domain that the user should use to sign in. The value of the domain_hint is a registered domain for the tenant. If the tenant is federated to an on-premises directory, Azure Active Directory redirects to the specified tenant federation server.