I suspect it is a MB bios issue.  In another system the issue was resolved after motherboard bios update.  I suppose Dell may release future 8940 bios update for this bug of DP. [URL] Re: Its very hard to find anything in relation to what my issue is online. see above discussion
I just bought an XPS 8940 a month ago and it is running an RTX 3060Ti.  When I use HDMI (gpu) to HDMI (monitor), no issues.  However when I use the Displayport (gpu) to the Displayport (monitor) I get the blinking light error code (on the desktop power button) of 3 amber and 2 white.  Which states that it is a graphics card issue.  Now running displayport to displayport seems to run everything fine, i get the correct resolutions and refresh rates.  However when i boot up the computer the Dell Logo (to get to the bios) does not appear and the monitor doesn't turn on until Windows is fully loaded up and at the login screen. Using different displayport cables yields the same blinking error.  Using the onboard graphics DP works with the monitor (no error code).  I talked to Dell support and they do not know what the issue is and are probably going to replace the graphics card and/or motherboard. ASUS support says send in the monitor for repair. I just received a replacement monitor off Amazon and its doing the same thing. I dont know what the issue is, as I dont think the monitor nor the graphics card/motherboard are broken. Does anyone know what the issue might be?
XPS 8940, ASUS TUF Ultrawide, no pre-Windows screens