Sumatra PDF is easily my favorite, but you’d have to use Wine.

I see, I got a WD Red Plus for myself for around that price, and it looks like that’s CMR. The base WD Red is SMR, though.

Yeah, the two things I’m willing to pay someone else to do is hardwood refinishing and drywall taping/plastering.

WD Red 4TB drives are only around $70 new, and they’re built for constant use in NAS devices.

Is there access to a cleanout from below?

Ideally, you’d want it anchored into a stud.