Did this at home last winter. Bulbs: pick ones with a documented local LAN API. WiZ bulbs take JSON over UDP port 38899, LIFX has its LAN protocol, both work from Python without any cloud account once they’re on your Wi-Fi. Around 10-15 GBP each.
The list is empty because the Switch can only send commands from the device profile’s Commands catalog. So:
1. On the Pi’s profile, Commands tab, add light.set, tier Basic, parameters room (Choice: hallway, living) and on (Yes / no). Boards send only Basic tier catalog commands, a Privileged one gets refused on a board.
2. On the Pi, handle v1/rpc/req/+, switch the bulb, answer on v1/rpc/res/{id}, and publish the real state as telemetry, as numbers: {"hallway_on": 1}.
3. Switch card settings: When this control is used, Run a command, device = the Pi, command light.set, room as a fixed value, on from the control’s value. Then bind Current state to hallway_on.
That last step answers David: the Switch shows what the Pi reports, so poll the bulb every 30 s or so and publish it, then a wall switch change shows up too. With a wall switch cutting power the bulb is just gone, so leave the wall switches on. Details on Control cards.