Feather STM32F405 Express
The new STM32F405 Feather that Adafruit designed runs CircuitPython at a blistering 168MHz – the fastest CircuitPython board ever. With a STEMMA QT / Qwiic port on the end, you can really easily plug and play I2C sensors.
With CircuitPython basics running on this board, it's fast to get all the drivers working, then use the built in plotter in Mu to instantly get sensor data displaying.
You can use MicroPython, CircuitPython or Arduino IDE with this board, with some caveats. Arduino is supported through STM32duino. This board and chipset is very new. You can expect developments and updates.
More information is available on the website of Adafruit.