Ahh I misread. I thought you had said DP to HDMI. No issue for that then unless its a really cheap nasty cable. Ive seen some cases of those not working.
There is a section in the technical guide that explains how to reset the bios. Its included in the Install Pack. You will need a USB key, formatted to FAT32, with the latest bios file (.bio). With the jumper moved to the right position, it will fully restore the bios using the update file on the key and reset it.
Thanks WD. I went down a crazy unnecessary rabbit hole this afternoon but I learned a lot about the NUC... and myself.
I messed around in BIOS some and stupidly enabled Fast Boot, which totally screwed me over. I couldn't get into BIOS. So I pulled the jumper and reflashed BIOS, only to be met with in the inability to get back into BIOS via F2 or F10. I found out that this is due to my monitor.
So my monitor problems are a known issue with Intel NUCs. It seems that when the NUC is connected to some monitors that are above a 1024x768 resolution, you may have difficulty getting into BIOS (per what I read on Intel's forums). My monitor is an LG Ultrawide; it's a totally messed up crazy resolution at 2560x1080. I was able in the past to get into BIOS but it felt very random and sporadic. I couldn't replicate it. Sometimes I could get in, sometimes I couldn't. After my reflash I couldn't get in at all.
My monitor has a feature called PBP (picture-by-picture) which allows for two machines to simultaneously be plugged in and both get displayed, giving me essentially two 1280x1080 screens on the same monitor. Switching to this configuration worked the first time... I was able to get into BIOS.
Once in to a totally refreshed BIOS I enabled a host of stuff to save my ass... boot to USB first, always prompt for a BIOS boot. Also, I figured out that my EFI boot weirdness was due to a setting I must have enabled in my idiocy... Boot > Boot Config > Boot Devices > Internal UEFI Shell ... I had that enabled and that's what was giving me the EFI shell boot issue. Disabling that, the NUC boots directly to Chimera.
Also, for anybody with a monitor resolution problem that makes it difficult to enter BIOS, I find enabling the "always boot BIOS first" switch does the trick. I can reliably get into BIOS now.
So my only other issue is with Bluetooth which, at the end of the day, is so minor that it doesn't even matter. I'm leaning toward my messed up secondary antenna as the culprit and I'll probably just pick up a USB BT receiver dongle to work it out. I love the Apple Magic Trackpad, such a pleasure to use, so I don't think I can stick with the standard USB mouse for too long.
What did I learn about myself, you might ask? I am so grateful that I no longer do this for a living. I've spent a lot of time troubleshooting this NUC/OSx86 project and it has been so much fun (frustrating but rewarding). Were I still doing IT as a career, I would have never even attempted this and I sure as hell wouldn't have spent so much of my free time troubleshooting something so inconsequential. I'm glad to recognize that my passion for computers is returning after a long slog of doing it professionally!