Fixing Coldboot Haxchi Bricks
This error screen is being is displayed when your Wii U is unable to open the installed title. It is commonly seen as a result of trying to coldboot to a title that was not properly installed, such as a Haxchi title for CBHC, when installing homebrew in 2017-2021. It is this combination of the title being unbootable combined with it being set to launch at startup that creates the unusable state.
But good news! As of 2022, this problem can be fixed, thanks to Gary's udpih exploit. To get started, you will need one of the following devices: