If you Google for 'Xiaomi Zigbee', you'll find lots of pretty good and affordable Zigbee devices. Ikea also sell a few now. However, I don't think many are directly supported by the Hue hub, sadly. I run Home Assistant on a machine that has a Conbee USB Zigbee stick plugged into it. That talks to all my non-Hue Zigbee devices, and Home Assistant makes it fairly easy to have, say, a Xiaomi motion sensor turn on a Hue scene. (The Hue motion sensors are good, and I have several of those too, but they cost three times as much). Many Home Assistant users dispense with the Hue hub altogether and just control the Hue lights directly. I haven't done that, just because the Hue hub has been so reliable for so many years that I'm reluctant to replace it with something more complex that my wife might have to deal with in my absence 🙂 But I may go that way eventually, and then all my Zigbee devices (dozens, now!) would be on the same mesh...