Prusa3D Core One assembled from kit ( https://www.prusa3d.com/product/prusa-core-one-kit/ ) in roughly 36 hours, including 5 hours of sleep and frequent toddler-herding
Quite fun and satisfying
I did make a few mistakes, but wholly my own, and avoidable by reading the actual instructions
Benchy test print (15 minutes) is complete, so I guess I can start planning holiday show-bag gifts for nieces and nephews
The assembly instructions PDF is 210 pages long.
If you own a 3d printer, imagine entirely disassembling it: take out every single screw, nut, bracket, motor, pcb, wire, bearing, belt, panel - literally everything to as individual component as possible - and put them all in a box. That box is what Prusa sends you when you buy a kit.