While Kubu sensors use Zigbee for local communication, they are designed to connect through the Kubu Home Hub rather than pairing directly with Home Assistant or 3rd Party hubs.
This is because Kubu devices use a proprietary implementation and device profile, so they are not exposed as standard Zigbee endpoints that Home Assistant can directly discover or control.
Kubu CAN however be integrated with Home Assistant via IFTTT rather than direct Zigbee pairing.
We provide various IFTTT triggers such as:
Door locked / unlocked
Door open / closed
Window secure / vent / open
Those triggers can then be passed into Home Assistant using IFTTT webhooks, allowing Kubu events to become part of wider automations.
So while direct local integration is not currently available, automation with Home Assistant is still achievable.
More info can be found via this link: https://www.home-assistant.io/integrations/ifttt/