Setting Up a GCC Toolchain For Programming Arduino In Plain C

I'm not an Arduino power user but when I decided to start with it I knew I wanted to program it in plain C and I knew I would buy a compatible board instead of the real thing just to take the feel of it. Probably because I'm a programmer, I found much more interesting to go down the rabbit hole of low-level details, datasheets1, etc., instead of letting the Arduino IDE and libs to hide things from me. I also didn't find of any use to learn a pseudo C++ when I already knew C. During these ...