Lets say I want to learn how to work on HPC problems. There's only really two ways tats going to happen. Working in an industry role on those sort of problems (which won't happen unless you already have that sort of background) or learning in in an academic setting (i.e. a University program)

I don't think self teaching via online courses or otherwise are realistic in this scenario because I as an individual don't have access to either the infrastructure or problem-sets at the sort of scale to work on this thing.