Hi,
I also have the Asus Strix 1080Ti OC installed on my Rampage IV Extreme. No issues ... except one small thing (which may be completely due to my setup, my specific card etc.) - every once in a while the graphics flicker for something linke one frame. Exactly half the screen seems affected (the effect is really in the far sub-second range, so I cannot tell for sure ...) judging from perception. The effect is that there seem to be colored horizontal stripes across half the screen (I have an ASUS 4k PA329Q display). The effect is rare (seen maybe once a week or once in several days at most), lasts maybe a tenth of a second or so and occurs during games as well as when using WIndows. No big issue in general, but I must say: My old AMD card did not have such instabilities. Currently I still suspect the NVidia driver, but who knows ... could even be a hardware problem. But since it is so rare and never "fatal" in any way I do not bother much and hope for the next driver version(s) to take care of it.
But in general: I have no issues with running the modern card on the RIVE.
Best regards,
Woelund