I’ve been working on the Aftermath kit from Kitbash3D, making it more Blender friendly. I think now that the best approach would be to add an empty in each collection of the original kit to parent the contents to and make it easier to manipulate each building (composed of many objects) as a whole. The problem with appending each building collection to another file is that all the textures get duplicated and it’s a PITA to clean that up.
Anyway, here I just took the kit as a whole, added a camera and a nice HDRI, lined it up with a decent shot and rendered away. I had some issues using Optix with Cycles. Kept getting error messages after the initial OK render. A bit of experimentation suggests that if the viewport is in solid mode it renders fine, but the problems come if the viewport is in rendered mode. I must remember that in future, as I tend to work on my scene in rendered mode if it’s not too slow.
I spent a bit more time on this and here’s the result. Interesting exercise.