I bought an Arlec smart fan. It has a WR4 wifi module inside, supposedly based on an RTL8710BN. These are now supported by esphome.

https://docs.libretiny.eu/docs/platform/realtek-ambz/#flashing

https://community.home-assistant.io/t/arlec-grid-connect-ceiling-fans/261127/67

https://esphome.io/components/libretiny.html

https://developer.tuya.com/en/docs/iot/wifiwr4module?id=K9605tvu78p3e

esphome:
  name: fan-1
  friendly_name: Sam's Room Fan

rtl87xx:
  board: generic-rtl8710bn-2mb-788k

# Enable Home Assistant API
api:
  encryption:
    key: "<snip>"

ota:
  password: "<snip>"

wifi:
  ssid: !secret wifi_ssid_2
  password: !secret wifi_password_2

uart:
  rx_pin: GPIO18
  tx_pin: GPIO23
  baud_rate: 9600
tuya:

fan:
  - platform: "tuya"
    name: "Speed"
    switch_datapoint: 1
    speed_datapoint: 3
    direction_datapoint: 4
    speed_count: 6


light:
  - platform: "tuya"
    name: "Light"
    switch_datapoint: 9
    dimmer_datapoint: 10
    min_value: 0
    max_value: 100
    color_temperature_datapoint: 11
    color_temperature_max_value: 100
    cold_white_color_temperature: 150 mireds
    warm_white_color_temperature: 400 mireds