Yes this is indeed a problem. You can get around this by piping the Z-Wave or Zigbee information into a MQTT server and basically run them as separate networks, with Home Assistant and MQTT tying it all together. But you will need some type of Zigbee to Ethernet adapter (Sonoff makes one, Raspberry Pi, etc.) or Z-wave to ethernet adapter (again Raspberry Pi). It's definitely clunky. But doable.

I am running multiple Zigbee networks near each other (in a house and in a detached garage) with Home Assistant, MQTT server and a Sonoff Zigbee bridge, with Tasmota.