TLDR; bad ram even though memtest gave a pass.
Alright, I spent about 14hrs on this problem so far. As posted above, I have 2 Samsung EVO 250GB 860s at my disposal. And then I started trying a Muskin 480GB SSD just for kicks and giggles. I went back to every release image from 4.15 to 3.03 and basically all of them had the same locking up as shown above.
I went ahead and tried to install Windows 10 thinking it could over-ride any errant UEFI entries in the BIOS after going through some Intel NUC forums, but received several bluescreens with different errors. So, I threw the RAM chips out and put in some small, but known good Ballistix 4GB…
HA image after burning, boots fine now. I will update on if this fix is permanent since a before a reboot would kill everything. But this is as far as I’ve gotten in several days so I’m keeping a positive attitude.