I just never switched away, my first computer was my dad’s old 2001 Sharp laptop running like lubuntu 12.04. I play around with Haiku and various BSDs sometimes, but I always end up with some Linux distribution as my main OS. Right now it’s NixOS on my laptop and OpenSUSE on my desktop.
Yeah krita definitely isn’t the right tool for bulk jobs. You might want to look into learning to use imagemagick’s command line tools, they’re pretty much the gold standard for bulk image tasks