I was a UNIX developer (kernel, as well as userland programs like troff) for 7 years, working for the first company to provide commercial support. (Our founder, the former head of the Cornell CompSci department, while at RAND, had them make legal arrangements for Western Electric to provide RAND with a commercial license for $20,000 for the no-support tape that they provided to universities for $300 ... from there the commercial UNIX world took off.) Later I started my Linux life with the Yggdrasil distro, my first of many. Nowadays, in retirement, I do development on WSL on Windows. (Getting a working and convenient emacs environment on it was a bit of effort but now it's how I do all of my editing.)