Of course it's Linux only, so means using WSL on my Windows laptop.
Managed to open the file, no instructions whatsoever for finding a compiler other than 'get the GCC one'. Okay. Found the mirror, downloaded it and just now reading the installation manual. Yes, it's a manual, basically. Two dozen prerequisite packages to install by hand before I do anything else.
It's guaranteed not to work on WSL so I'll have to spend an hour or two just getting a compiler up and running, that's assuming it works at all and I don't just have to fire up a Debian VM and start again.
I get C is hard, and is supposed to be hard, but it's like GNU are going out of their way to make this intentionally more difficult than it needs to be.