Today Kristian added support for STM32F4-based NUCLEO-F446RE board. The board is available from the manufacturer for little more than ten bucks which is pretty good for this type of MCU. The commit can be examined here.
Even though NUCLEO claims Arduino compatibility the 2×3 SPI connector is absent. It means that many modern Arduino shields, including full-size USB Host Shield, won’t work on this board. For his setup, Kristian used USB Host Mini wired as described in Teensy 3 wiring article. More information is available in the example repository on Github.
Thank you, Kristian!