Tested in practice in this project. Small add on board to use the 4bit SDIO directly on the Teensy4.0 at the cost of the usb host pads,
Kicad 8 project including gerbers.
github.com
Kicad 8 project including gerbers.
GitHub - hexeguitar/Teensy40_SDIO_adapter: Small SDIO adapter as solder on module for the Teensy4.0
Small SDIO adapter as solder on module for the Teensy4.0 - hexeguitar/Teensy40_SDIO_adapter
github.com