> It's not as though I can do a COBOL side-project to learn... or can I?

My first job out of college - around '94 or so - was working for an accounting software company that sold an accounting package written entirely in RM Cobol for DOS. The entire UI and the backend were all written in Cobol. Poking around a bit, it does look like GnuCobol (https://gnucobol.sourceforge.io/doc/gnucobol.html) allows for some screen I/O… so you could put something together on your own machine.