A company wantsto provide its employees with a custom mobile app that accesses Salesforce.

Configuring Mobile App settings in connected app and Salesforce as identity provider for non-Salesforce internal apps is the best way to meet the requirements with the privately distributed mobile app. The Mobile App settings allow users to download the app from a private URL and use it with Salesforce credentials. The identity provider settings allow users to access other internal apps with SSO using Salesforce as the IdP. The other options are either not feasible or not optimal for this use case. References: Mobile App Settings, Single Sign-On for Desktop and Mobile Applications using SAML and OAuth