ETU seems to work as intended on my SB2 and able to reach over 4k in Geek5 with ETU UV -0.1v
https://i.imgur.com/7nMwvaX.png
but you need specific build, otherwise, you will get the above error-code.
Was pleasantly surprised to see my low'end fanless SB2 top Geek4 on all the top 8 ranking...