A cloud-based identity and access management service for securing user authentication and resource access
At this time, it is not. Please refer to the note in this section of this documentation:
While it's not possible to setup OAuth on the non-gallery applications, you can manually generate an access token from your authorization server and input it as the secret token to a non-gallery application. This allows you to verify compatibility of your SCIM server with the Azure AD SCIM client before onboarding to the app gallery, which does support the OAuth code grant.