Yes, it's true, but it's simply impossible to find a paying job doing BSD or Solaris these days.

I mean, even if you get a job at Oxide Computer, what do you do if you decide to move on because of your manager or whatnot?

Literally all the sectors are Linux now, you'd think BSD would be huge in embedded because of licensing, yet it's still Linux. OpenWrt is Linux, Android is Linux, OpenIPC is Linux, not to mention the entire data-centre stacks being all Linux now.