[Mashiro]

Thanks for the feedback / answers to my previous question.

So the Intel Core i3 8100 system uses a different mainboard with a different chipset. Given that the 2060 works on this system I don't think it is the CPU, RAM or PSU but rather something related to the mainboard and GPU combo in the Intel Core i5 9400F system. Cannot really prove it though. I have no to little experience with newer Intel systems as my first and only Intel PC was a prebuild one with a i5 6500 (older than both of your systems) and the OEM components had pretty much no labels or anything that would give hints to chipsets and such things. Maybe a different mainboard with the same RAM, CPU and GPU might do it?

On the other hand there is some kind of chance though that maybe the PSU on the i5 9400F system combined with the 2060 is having some kind of issues maybe? The AMD RX 470 is nothing compared to the 2060 in terms of power requirements and power usage. So that is the reason why it might work. You could test a different PSU in the i5 9400F system. Overall I think Corsair is a very reliable brand and I have used them before flawlessly. So I still kind of don't believe that it is the PSU.

To me it smells like there is some kind of incompatibility between atleast two components. Don't have enough experience or resources to reproduce or prove it though.