High kernel_task CPU Usage is due to high chassis temperature caused by charging. In particular Left Thunderbolt port usage.

Solutions include:

  1. Move charging from the left to the right side. If you have a second charger then plug it in on the right side. Avoid plugging everything on the right side (see last paragraph below).
  2. Unplug something from the left side. Either power or another accessory until the battery is full.
  3. Force fans to max before plugging in. iStatMenus has an easy Sensors -> Fans menu item to do so. This only helps in marginal conditions.
  4. Move to a cooler room.

Just so happens that my set-up is such that I can only charge using the right side TB3 port, now let’s move on to finding the next obscure solution to the next MacbookPro issue.