MQTT client controlling remote 433 MHz power switches using NodeMCU for ESP8266. Tested with Telldus and Nexa devices using the self-learning protocol. The RF module was written as the built-in library of NodeMCU doesn't work with the aforementioned devices. Any 433.92 MHz ASK transmitter module shall work.

For controlling the remote switch using Home Assistant, enter the following in your configuration.yaml:

switch:
  # Switch 1
  - platform: mqtt
    name: "Displayed name of switch 1"
    state_topic: "home/lamps/switch1"
    command_topic: "home/lamps/switch1/set"
    payload_on: "{ \"addr\":1, \"unit\":1, \"onoff\":0 }"
    payload_off: "{ \"addr\":1, \"unit\":1, \"onoff\":1 }"
    optimistic: false
    qos: 0
    retain: true
  # Switch 2
  - platform: mqtt
    name: "Displayed name of switch 2"
    state_topic: "home/lamps/switch2"
    command_topic: "home/lamps/switch2/set"
    payload_on: "{ \"addr\":1, \"unit\":2, \"onoff\":0 }"
    payload_off: "{ \"addr\":1, \"unit\":2, \"onoff\":1 }"
    optimistic: false
    qos: 0
    retain: true
  # Switch 3
  ...

Note: The onoff field is inverted, which could be seen in the rf.lua file.