The integration of OIDC is very limited and tailored around the use of Auth0. The implementation is not done according to the standard and therefore is only usable with Auth0. Other IdP (like Azure) can't be used because the Implementation needs Fields that are not available in Azure.
The field that makes problems is the siganture. In Auth0 this is a static certificate and the content of this certificate can copied into Absorb. In Azure the certificate changes periodically (daily) but can be retrieved via a URL. Generally all the information needed for OIDC is described in a metadata endpoint.
Sources:
Azure and OIDC: https://learn.microsoft.com/en-us/azure/active-directory/develop/active-directory-v2-protocols
Example Metadata-Endpoint: https://login.microsoftonline.com/common/v2.0/.well-known/openid-configuration
Signature mechanism: https://learn.microsoft.com/en-us/azure/active-directory-b2c/tokens-overview#validate-signature