To add to this, I wonder if a properly designed case could create a chimney effect (not unlike the crossdraft kiln Primitive Tech made in his most recent video) where escape heat is drawing in cooler air in such a fashion as to be adequate enough fo the vast majority of applications.
Not that fans need to be very loud, or even spin very fast for something of this size, I imagine relatively low RPMs (probably sub 100 RPM) could still achieve considerable cooling, especially with a crossdraft optimized case.
This is why I suggest in the video to just stick some ventilation holes in the top cover. Instead of the heat pooling in that area, it could escape, and there would be some natural convection—in through the gaps around the ports, out through the top. It wouldn't be as good as a fan, but definitely better than slapping a heat sink inside the case.
My plan was to just use a Dremel to notch some holes in the top of the case I ordered a kit with... I just ordered another case that has a fan and will try that... the new one will probably take over retro-gaming chores and I'll find something else for my 3B+ to do.
The case has small rubber feet on one side and the case is slightly dome shaped on the other, I think people will be able to place it correctly without an explicit instruction, plus there is only one “right way” to place it as it is already.
It would work for most people, wouldn't it? And the people putting their raspis into unusual scenarios for which the case was poorly suited could simply choose to not use that particular case. Encouraging thermal convection (ideally flowing over a proper finned passive heatsink) with a chimney design seems like a pretty good idea to me.
Not that fans need to be very loud, or even spin very fast for something of this size, I imagine relatively low RPMs (probably sub 100 RPM) could still achieve considerable cooling, especially with a crossdraft optimized case.