what would be a typical salary range for 1 year kernel dev + 4-5 years in related experience? let's say BayArea/NY/Austin? I really did like learning about kernel dev before. Might be time to learn again..
That's less than somebody with 0 years experience in FAANG will make. I wouldn't expect kernel developers to get paid much differently than non-kernel developers at a similar level.
It's really just down to location, then. They vary so much, and I don't have a lot of experience in the locations you mentioned. You can expect high-end software engineering salaries for good kernel hackers.