How to access different endpoints?

Yes, but unfortunately setting Association Group 1 to “OpenHAB Controller” makes no difference. It also makes no difference how the device was included (directly via ZStick or via Habmin). Receiving state updates of switches/dimmers may have worked in the past for you, but it is not working in stable 2.1.0 and neither in current 2.2 snapshots (or at least for devices included in those releases). The problem is more generalized, see this thread: Status updates for Qubino Relays/Dimmers generally do not work