I don't think I've seen it mentioned here before, but I found a source of free 3D models yesterday - SketchUp 3D Warehouse. Seems to be a place where hobbyists upload their stuff, and reading through the T & Cs it looks like you can use the models for any non-commercial use.
Here's a free computer I found
I got a couple of semi trailer rigs, and there's also some half-decent city scapes eg NYC here
the sketchup files have skp extension, and you can just drop them into cinema, although I've found that if there's a choice of versions an older one (say 2014) works best.
https://3dwarehouse.sketchup.com/index.html
apologies if this is old news - it's new to me