I’d personally look for a used Prusa i3 MK3[S[+]]. Part of that is personal bias, it’s what I still print with (specifically the MK3S variant, I haven’t bothered to upgrade it to +), but in all the years I’ve had it it’s been an absolute workhorse and has very much thrived on the copious amount of neglect I’ve given it. The only thing I’ve ever done to it is install firmware updates and occasionally smear some grease on the smooth rods with a finger. Still, every time I print with it, it just works.

Prusa just announced a new printer so there might be a little wave of them being put up for sale.