> I've never used or even seen a mainframe in 26 years in the tech industry.

40 years here. Although in theory I've used a mainframe in college, but it wasn't IBM (Burroughs) and just seemed like "a computer" at the time. I also worked a bit on a terminal emulator for ICL mainframes, so probably at least logged in. So 40 years of saying "I wonder if the mainframe people already have a solution to this?"

Probably mainframes haven't been much used for HPC since the transition to Cray in the 70s.