Actually
a reset of the BIOS would not help, all that would do is make it start monitoring the CPU fan again once set to ignore it because it does that by default.
You'd want to set things so it ignores the CPU fan and then
save your settings.
However since the GPU swap didn't change much of anything except it booted with weird graphics I'm beginning to think the board is defective in some way. Again, the deal with it's RAM could be a part of it but at this point, since it did boot and show something on the monitor that's probrably a non-issue in itself here.
As for a fan, any fan that can be plugged in that fits the CPU fan header will work, you can even use one of the case fans if it will reach this header - As long as the board is reading a "CPU fan" that will take care of the potential CPU fan detection problem. Essentially you're tricking the system into believing it has one plugged in and it will work provided that is the root of the problem here. Set it to ignore the fan, save and then you can unplug the fan once you've verified it's working and ignoring it.
If all else fails you may want to start looking into an RMA of the board.
I have to assume you've already taken care of it but if not, you may want to. I've circled where I saw a streak of TIM between two components on the board.
BTW, what is that in the RAM slot towards the bottom right of the pic?
Anything in the slot can make it not work.
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