Attempting to add a private endpoint to API Management service displays the message: "No available items" and "No supported sub-resources"

Problem

You attempt to configure a private endpoint for an API Management service but unable to select any Target sub-resource in the Resource configuration:

The value must not be empty.

No supported sub-resources

No available items.

Solution

For this environment, the issue was that the APIM was deployed on the stv1 compute platform:

One of the prerequisites as listed in the Microsoft documentation (https://learn.microsoft.com/en-us/azure/api-management/private-endpoint#prerequisites) is:

The API Management instance must be hosted on the stv2 compute platform.

To correct this and keep the APIM in the developer tier, we would need to deploy the APIM within a virtual network (VNet) and select a public IP address during the deployment process:

Once the APIM was placed into a VNet and upgraded to stv2, we would then need to remove the APIM from the virtual network by setting the configuration to None as the option would not be available if the APIM was in a private network.