It’s exactly as stated inside the OptiX Release Notes: “DMMs are supported on GPUs with RTCores and accelerated in hardware on the new Ada Lovelace generation of GPUs.”
Means they are not available on GPUs without RT cores.
If RT cores are present on a GPU can be queried inside an application at runtime with optixDeviceContextGetProperty and the OptixDeviceProperty enum OPTIX_DEVICE_PROPERTY_RTCORE_VERSION.