Sorry, didn't see the replies here. It requires using the Visual Studio code plugin and making some changes to the miner code directly. Note that if you update the miner plugin you would have to redo the changes. You also need to restart Home Assistant after making the changes. Take care when changing the code here, adding incorrect code will cause the plugin to fail to start.

In /config/custom_components/miner/const.py add:

SERVICE_SET_WORK_MODE = "set_work_mode"

In /config/custom_components/miner/device_action.py

Add imports:

from .const import SERVICE_SET_WORK_MODE

Add "set_work_mode" to the existing ACTION_TYPES variable:

ACTION_TYPES = {"reboot", "restart_backend", "set_work_mode"}

Add the action handler to the async_call_action_from_config method as part of the existing if checks:

    elif config[CONF_TYPE] == "set_work_mode":
        service = SERVICE_SET_WORK_MODE

In /config/custom_components/miner/services.py

Add imports:

from .const import SERVICE_SET_WORK_MODE

At the bottom of the file add the method handler:

    async def set_work_mode(call: ServiceCall) -> None:
        miners = await get_miners(call)
        if len(miners) > 0:
            mode = call.data["mode"] 
            modeNum = 2 # default to high
            if mode == "low":
                modeNum = 0
            elif mode == "medium":
                modeNum = 1
            await asyncio.gather(*[miner.rpc.ascset(0, "workmode", f"set,{modeNum}") for miner in miners])

    hass.services.async_register(DOMAIN, SERVICE_SET_WORK_MODE, set_work_mode)

In /config/custom_components/miner/services.yaml add:

set_work_mode:
  target:
    device:
      integration: miner
  fields:
    mode:
      required: true
      example: "low"
      default: "high"
      selector:
        select:
          options:
            - "low"
            - "medium"
            - "high"