21.02.3: https://firmware-selector.openwrt.org/?version=21.02.3&target=ramips%2Fmt7621&id=xiaomi_mi-router-4a-gigabit
22.03.0-rc6: https://firmware-selector.openwrt.org/?version=22.03.0-rc6&target=ramips%2Fmt7621&id=xiaomi_mi-router-4a-gigabit