AFAIK neither Unreal nor Unity will frustum cull the triangles of a model out of the box and although both offer some other forms of occlusion culling they also only operate at the whole model level.
This is wrong. Unity has frustum culling enabled by default. You are correct that it only operates at whole model level though.
Occlusion culling in Unity is fairly straightforward. Simply requires a bake. It also supports 'occlusion areas' where you can give it a hint to do a higher resolution occlusion bake e.g. if you think the player will likely be in that area.
Edit: originally misread parent as stating Unity didn't frustum cull by default. Parent comment is correct.
I’m not wrong just being more specific. All three engines frustum cull by default and all three do it at the level of the complete model. I said Unity and Unreal don’t frustum cull at the level of the individual triangle which was the factor the person I was replying to insinuated Godot lacked.
Occlusion culling in Unity is fairly straightforward. Simply requires a bake. It also supports 'occlusion areas' where you can give it a hint to do a higher resolution occlusion bake e.g. if you think the player will likely be in that area.
Edit: originally misread parent as stating Unity didn't frustum cull by default. Parent comment is correct.