The way I tested was search Thingiverse for "angular" and download an STL, then convert it online to an OBJ on the first search result for "stl to obj"

Specifically I tried this rook from this chess set. https://www.thingiverse.com/thing:5994219/files

Sadly, some of the crenelations on top of it are just cubes with 2 sides missing that would be impossible to attach to the folded up rook. I imagine there is a ton of loss between a file for a 3D printer, a random convert to Obj with no settings, and this net maker, so I'm not unsympathetic to the problem. It's just that this is a printout that would not be foldable into something useful.

Some items on thingsverse provide .obj files; like the king in this chess set...

https://www.thingiverse.com/thing:1078513/files

or this army tank...

https://www.thingiverse.com/thing:4618182/files

(n.b. under the main image viewer click the "files" tab to explore individual files/extensions)