It depends on the role. My first job was doing manual QE on Windows, and knowing Linux wasn’t much help at the time, but it did help me transition to a coding role in the same company a year later. I’m now doing platform engineering at a major tech company, but that has a high barrier to entry, which I suspect is the case for most roles that are Linux-focused. If you’re trying to get your foot in the door, I think you should look at job profiles for low barrier to entry roles (e.g. tech support) and try to work your way up.
I hope he sticks with it. Insuring his collection could be a sticking point, but he may get you into sticky situations without insurance. I’m sure he’ll find an agent to stick up for him.