Also, I too wanted to extend to you a really big THANK YOU from a very happy member of the HASS community. I came over from OpenHAB a handful of years ago and I couldn't be happier. Please keep up the good work! Good luck with all the hardware sales and Nabu Casa stuff!
edit: clarified that I used to run OpenHAB
In real terms though, it not that bad. I've got about 25 such devices always online and the traffic really is negligible. Most devices aren't sending anything while nothing is happening except for the periodic heartbeat like once a minute. Its not noticeable, even on my 20MHz wide network.
i'm personally avoiding wifi devices now and holding out for matter/thread variants
I’ve managed to bind them using Matter bindings, so even if HA is offline, the switches can still on/off and dim the bulbs.
No UI supports this yet (though I think HA is working towards it), but the underlying protocol support exists, and products are starting to come to market that take advantage of it.
I think it 2-4 years, it’ll probably be ironed out and working well, but if you really want it, you can have that now with matter/thread.
I think Zigbee devices also have bindings, and those should probably be a lot more mature, but I haven’t played with those yet.
I have 100% Zigbee lights, and each lighting circuit has a Shelly Plus 1 with the relay in "detached" mode (so the shelly will sense the light switch changing from open to closed and send a command to HA to turn on the lights via Zigbee). Most (all?) smart bulbs have a setting for "what do I do when power is restored" and you can set it so that they come on when power is restored.
You can then create a script that uses the MQTT HomeAssistant up/down topic and if HA is down, when the switch changes position operate the relay.
It's not perfect - if you have a powercut during the night all of your lights will come on when power is restored.
Will look into Shelly
Perhaps have a look! Thanks for all your work again, I love HA