Feather M4 Express featuring ATSAMD51. This feather is powered by our new favorite chip, the ATSAMD51J19 - with its 120MHz Cortex M4 with floating point support and 512KB Flash and 192KB RAM. ...
The most exciting part of the Feather M4 is that while you can use it with the Arduino IDE ... it's even being shipping with CircuitPython on board.
When you plug it in, it will show up as a very small disk drive with main.py on it. Edit main.py with your favorite text editor to build your project using Python, the most popular programming language. No installs, IDE or compiler needed, so you can use it on any computer, even ChromeBooks or computers you can't install software on. When you're done, unplug the Feather and your code will go with you.
But still no proper debug connector.