i'm currently having the same issue with mine. have contacted support. done the same things you have done with no resolution. ive also gotten a message pop up when the system loads that says " hardware change detected. gpu not overclockable"

Reset the power setting back to default and reboot. I messed around with power settings by stopping hibernation, changing times to sleep etc and had this issue.  Went back to default and no problems for weeks.

I tried resetting my power settings but I'm still have this issue. I've been just shutting the PC down each night and havent had to deal with the issue, but today when I turned the monitors off for 15 minutes for a work meeting, the signal to the monitors just stops. I think the PC is freezing when the monitors turn off, and I made sure I got in brand Alienware monitors. Pretty stupid problem for the price tag of the PC.

I'm disappointed with the aliens, I'm having the same problem so far, there's no way to fix it, I won't be buying any Dell products in the future