The Changelog Podcast had a good talk with someone who teaches mainframes and helps people get jobs.

"This week we’re talking about mainframes with Cameron Seay, Adjunct Professor at East Carolina University and a member of the Governing Board of the Open Mainframe Project. If you’ve been curious about mainframes, this show will be a great guide." https://changelog.com/news/mainframes-are-still-a-big-thing-...