Adafruit FeatherM0 ASF Tutorials
The tutorials in this section try to explain how to use different functions of the Atmel ATSAMD21G18A based Adafruit FeatherM0-WiFi board, using AtmelStudio and the Atmel Software Framework (ASF) only.
You will need an external Programmer/Debugger for this to work. The Atmel ICE SAM works great for me.
Read FeatherM0_WiFi - An Odyssey if you are interested in how to hook it up.
These tutorials are about how to work directly with the SAMD MCU on-board. So you don't need a bootloader, just the bare hardware.
The source code for the tutorials can be found on GitHub.