Heh nah, I already had linux installed (not using secure boot) and verified I was actually booting into it by logging in through SSH.
Sadly I don't have onboard graphics to try. BUT.. the problem solved itseld (see further down)
There shouldn't be anything in the buffer if you turn the system entirely off, it's volatile memory.
That's what I thought...
Anyway, for some reason the card now works and still I can't make any sense of it.
I tried powering off for a while to let things cool down completely. NOTHING.
I tried switching the PSU off for a few hours. NOTHING.
I tried reseating the card into the pci-e slot. NOTHING.
I tried a different HDMI port. NOTHING.
I gave up, left it over night. Next morning? still NOTHING!
Contacted sapphire and amazon, and long story short, amazon said they'd refund me (even tho it's way past the 30 day return period.)
Then tonight, just now, I decided to give it one last try before packing up for return. Nothing was changed besides the system being down for even longer than I tried before (more like 24 hours, previously it was around 10)... IT WORKS!
Really really weird. Good that it works, sucks that there's no explanation but even tho it works, I might consider returning to amazon anyway. I can rebuy a fresh card, or even upgrade using the mined coins + the refund.
Still deciding what to do but for now, some more mining.
Thanks for the suggestions guys, sorry I don't have a better explanation as to what the heck happenend. I'd LOVE to know how something like that can resolve itself.