I have seen another post here where someone is having the exact same issue as me but with an Asus x570e board.
My current new build is with Asus rog strix x670e-A board. I am running a 4080 and my monitor is a Samsung Odyssey Neo g7.
The issue is simple to replicate and that is if I enable windows safe mode and restart, monitor goes into a standby loop and never goes into windows. Or if I restart my pc and press delete to get into bios, the monitor again gets stuck in standby mode. In both scenarios the pc is running as I have checked with another monitor and when I take the HDMI cable out of my 4080 and plug it into the integrated gpu.
I have also returned my monitors once and bought them again from another vendor. I just don't think its anything wrong with my pc or monitor as both on their own work perfectly fine. In addition, using the same monitor I can easily get into safe mode and bios but of course I have to change disconnect from my 4080 and use the integrated graphics. Annoying to say the least as I just want to be able to access both the safe mode and bios whenever I want w/o having to swap cables around.
Has anyone found a solution to this? I think its to do with the display signal not being picked up by the monitor from the GPU when going into safe mode or the bios due to some incompatibility. Can't figure this one out. May be it is specific to RTX 4000 series or just a general issue with high performance monitors that are too sensitive to pick signals up in these modes.