Live in a farm with many buildings. Problem: its long distance (20-40 m) and sheet metal. I have ethernet cabel to all building. I bought Tp-link M9 plus (have zigbee roter inside), but misunderstand how it works. Have try with Ikea tradfri-bulb. Not work.
That would result in multiple coordinators with dedicated Zigbee networks. No problem with that, except binding two devices (switch and bulb) directly via Zigbee won’t work. It will of course be possible using Home Assistant.
Zigbee is about density, you sure you can’t use intermediate smart bulbs, sockets or other devices on mains?