My Recommended Kubernetes Resources for Newbies

Recently, a friend of mine asked me what resources I'd recommend to start learning about Kubernetes. He was a victim of the layoffs that seem to be so prevalent right now and has experience as a classic SysOps / SysAdmin engineer but no expose to Kubernetes yet and wanted to learn to help improve his job-hunting prospects.
I wasn't sure what to recommend at first, it's been a long time since I was learning Kubernetes for the first time and wasn't sure what was still useful and relevant but what follows is what I ended up sharing with him, and now with all of you.