I was recruited directly out of a feeder school (University) for this company after focusing my undergrad course selection on operating system topics.

Compared to twenty years ago, there are significantly fewer operating systems which means fewer companies have a need for this type of work. If you're looking to get into this work I'd suggest looking at Apple, Samsung, Nvidia, Qualcomm, Google, Microsoft, Arm, and any Arm architecture licensee. It seems that the people with the most luck these days end up tinkering with Linux at university, do a Google Summer of Code project and score an internship with one of the above.