OIDC Signature verification function not compatible with generic OIDC provider

I have configured my SaaS instance to use OIDC authentication and configure an Oracle IDCS as IdP (as used by the customer).
When the gateway tried to parse the well-known endpoint configuration this results in an error

remote_v2.lua:261: oidc_issuer_configuration(): invalid OIDC Provider, expected application/json got: application/json;charset=UTF-8