A google search showed me this page. https://www.ibm.com/case-studies/ibm-academic-initiative-sys...
IBM has quite a few training and certification programs available [1][2][3][4]. (Number four is quite interesting: a yearly competition designed to teach mainframe skills.)
From my understanding, Java development on the mainframe isn't significantly different from standard programming. Much of the heavy lifting happens in the background, and the programmer's focus then becomes learning the ins and outs.
As for compensation:
https://www.glassdoor.com/Salaries/mainframe-developer-salar...
https://www.glassdoor.com/Salaries/software-developer-salary...
Mainframe dev: $74.9k. Software dev: $76.5k. Seems fairly equivalent.
> You touched a bit on dying workforce when you mentioned COBOL. Is that dying workforce a real problem making it financially lucrative for the people willing to learn that stuff? Or is it just a myth?
All good myths rely on elements of truth. :)
Will there be COBOL positions? Sure, for at least 10-20 years. But how do you want to set yourself up for additional growth?
If you invest time to learn traditional blacksmithing techniques, you might find a job at an interactive museum or on some specialized YouTube channel. Nothing wrong with that. Can't say there's lots of growth in that industry, though. The time and effort invested is about preserving the methods of the past. So, are you looking to preserve or create? Either option is perfectly fine, but each presents tradeoffs.
----
Sources:
[1] https://www.ibm.com/certify/
[2] https://www.ibm.com/case-studies/ibm-academic-initiative-sys...
Let's say I want to focus on developing, maintaining and running the software on mainframes. How do I get "in" and are the skills paid well in comparison to a typical Java/.NET/C++ developer position nowadays?
You touched a bit on dying workforce when you mentioned COBOL. Is that dying workforce a real problem making it financially lucrative for the people willing to learn that stuff? Or is it just a myth?