Using the sample code from this article, I've been able to connect to IoT Hub using DPS with a Group Enrollment based on X509 certs. However, using the same code and certs to connect to Central, the registration fails with:
ProvisioningClient RegisterAsync...Failed Custom allocation failed with status code: 401 ProvisioningClient AssignedHub: ; DeviceID: Failed to register device
In both cases (DPS and Central) the Root certificate has been uploaded and verified successfully.