struggling to understand where to start with an effect trying to follow a (non-tutorial) video.

[molten kiln]

I found this video showing and explaining exactly what I want to do in Unity but they didn't share the source code for me to understand where to start.
as for written shaders I only have experience with compute shaders so I don't even know what kind of asset to make to get started to try to follow along.
the theory makes complete sense but I just can't figure out how to start implementing it.
https://youtu.be/Mp7eQsiZ_wA?t=203 here's the video in question

[spare pivot]

As far as I can tell you don't need anything special for "crisp" pixel 3D renders, and the explanation is not quite correct
URP has a setting for decreasing render scale with nearest neighbor upscaling, which is identical to the result here but it also saves performance because it lowers the source resolution, skipping the need for downsampling a high resolution source
At 3:00 "enlarging the render does not result in a crisp image" but it visibly does, the Game window uses the very same nearest neighbor upscaling
The softness comes instead from antialiasing in the source render, which you'll likely want to disable entirely when rendering something in this pixelated style
I expect render scale can be used to get any input resolution you want, but alternatively you can render to an RT texture of fixed resolution with nearest neighbor filtering if needed

[molten kiln]

I believe the decreasing render scale says it doesn't allow the use of the depth buffer anymore.

[spare pivot]

Where does it say that, and "use" in what context?

[spare pivot]

Which editor version that happens in, and with what target platform? I've never seen that warning before and can't find references to it
It mentions the game view so sounds like it might only concern the editor