While I do not have any personal experience with these alternative options, there is a whole guide thread here on the forum
Depending on how you get your IRK it might be in HEX format, you will have to convert it into base64 for usage with Theengs Gateway.
Currently this is limited to Theengs Gateway, but might also be added to OpenMQTTGateway in the future.
I think I might have mentioned this to you before with your BM2, you can either install the esp32dev-ble-mqtt-undecoded binary on all your ESP32s so that they all function as remote Bluetooth reception antennas only, forwarding the undecoded messages to a central Theengs Gateway which does all the decoding, including this Apple devices implementation, or you can just convert your exiting OMGs by publishing
{"extDecoderEnable":true,"save":true}
to the
home/OpenMQTTGateway/commands/MQTTtoBT/config
topic.
By using one or more undecoded OpenMQTTGateway gateways like that you can make sure to have a reliable coverage over a wide area.