Sorry to hear your problems.
I'm also the guy in the other post where I can't make it work/POST with more than 2 GPU's
I've also tried before bios update and after. Nothing seems to do it's thing.
I used the same hardware except the m.2 in an 2013 Rampage IV extreme.
This is really annoying.
Let us know if anything changes. Seems like you've already done a lot.
AMD Ryzen Threadripper 3960X
ZENITH II EXTREME
Corsair 4x16GB Vengeance RGB PRO -- CMW64GX4M4C3200C16
GPUs:
EVGA Geforce GTX 1070 Founders Edition -- EVGA Geforce GTX 1070 Founders Edition -- EVGA Geforce GTX 1070 SC -- Geforce RTX 2080ti - Driver: 441.28
C: Samsung ssd 970 Evo Plus Nvme 1 TB WDC 2002FAEX - hdd 2tB
WDC 4003FZEX - hdd 4tB -- WDC 1001FALS - hdd 1tB WDC 2002FAEX hdd 2 tb -- ST10000dm0004- hdd 10 tb -- Samsung ssd 840 Pro Plus Nvme 256 GB -- Samsung ssd 850 Pro 512 GB