Neither did I, until recently. You can integrate their current cloud based hub, and I know @SteveBarcus is planning to update the integration for the new local hub. There's also an HA cloud integration and that community is also working on an integration with the new local hub (so HADB is an option for that method too).
For my mailbox, I bought a Yolink Relay and configured it for a Device to Device (D2D) connection. Then connected a zigbee button to the relay.
I first had a contact sensor on my mailbox, but have since switched to a motion sensor. There was a deal on two motion sensors and their existing cloud-based hub, so I bought that (and at the price I paid, the hub was essentially $4). Even though devices can be joined D2D without the hub, their motion sensors only report active. To make the relay return to OFF by itself when triggered by a motion sensor, you have to set it into their "Pulse mode". This requires their hub to configure that, so I needed it anyway for my use case. I have the hub integrated with Hubitat, but just for fun. Don't need it for the mailbox trigger now that everthing is setup.
