The Platypush support for HomeKit is quite limited because I don’t use any Apple devices and I’ve never had the chance of testing it properly. From what I understand however HomeKit supports a limited set of Zigbee bridges while Z-Wave support is very limited. However, if HomeKit can subscribe to some MQTT topics then what you can do is to forward Z-Wave events to an MQTT broker — it shouldn’t be needed for Zigbee, since Platypush already leverages Zigbee2MQTT.
If instead you’re looking for a more native solution, I’m not sure how to advertise the emulated bridge like a bridge compatible with HomeKit, but if anyone has experience with HomeKit development then I’m very open to pull requests.