Depends on the bulb. Philips Hue for instance work fine as a dumb bulb if there is nothing to pair with. And (at least some) have Bluetooth so you can connect them that way to your phone in ther interim.

There is no set rules, and will depend on the bulb. But I had a few for a while that I just used as dumb bulbs until I fixed my setup.

I use this combo with OpenHab instead of HA, but the relevant bits are all the same.

I find it pretty good, but have had these problems:

• Really poor Comms with devices: this turned out to be the placement of the dongle, it was too close to my PC case, and putting it on an extension resolved this completely.
• Rarely (once a quarter ish) the controller will fail to communicate with Zigbee2MQTT, causing the latter to crash. I’m not on the latest version of either and probably should update, but simply have the Zigbee2MQTT process (using a docker image) restart automatically and it’s not something I notice any more.
• Even more rarely (I’ve had it once) the dongle crashed to the point that I had to unplug it and plug it back in to restore service.

It’s by far more reliable than some of my questionable scripting choices 😊

Not really. I had a major update to OpenHab which to be frank, isn’t the best at regression and backwards compatibility, and that kippered a lot of stuff, but once I had worked through those everything was back to normal.

Batteries run out, and sometimes kit can fail (touch wood I haven’t had that).

Though I think if you go down the commodity route with a mixed in ecosystem, you’re more likely to hit issues over a more involved system.