Try connect monitor to VGA video provided by 7010. https://www.dell.com/downloads/global/products/optix/en/optiplex_7010_technical_guidebook.pdf

For some reason iGPU video output may suffer a delay during POST, thus you do not see splash screen or bios.

If still no access to bios, try reset bios jumper on motherboard.

Ok so I reset the jumper following these instructions. I followed nr 3. "How to clear the BIOS, CMOS or NVRAM, Via a Jumper on a Desktop System Board Only"

Still no success. After I press F2 when I start up the machine, the led monitor keeps blinking and the panel won't turn on, still remaining black. 

So I guess that leaves us with a VGA monitor, but it would be a little silly to just buy a VGA that I otherwise wouldnt need. But I'm in the market for a GPU that will drive 4k instead of a vga monitor, could this kill two birds in one stone if you know what I mean? Or are desktop pc's in their nature so that you always have to use the stock video output to access BIOS?
Im sorry that Im so illiterate when it comes to normal pc hardware. I used to use macbooks all my life.

You do not have to rely on vga to access bios. Try change CMOs battery $1-2 to new one and see it helps.  If you want to try get video from a discrete video card that is another option to test.  it seems after resetting CMOs the pc responds to F2 partially but still unable to give you bios video.  If you do not press F2 it still proceeds to boot without splash screen, correct?

try the following as another way to enter BIOS

https://www.laptopmag.com/articles/access-bios-windows-10

I tried a couple of things. 

1. Looked at the article from laptopmag.com. I didn't get the option from the article "Advanced". From the article I need the "UEFI Firmware settings". But here is wat I got instead:

2. I changed the CMOS Battery, but only as an experiment. Meaning I didn't have a new battery laying around neither did I have a store nearby. So I tried a battery off a guitar tuner maybe it had a little more juice that could make the difference. But it didn't. What I did do though was leave the battery out for 5 mins see if that did anything, but the situation is still the same though. 

Try disabling fast startup. 

https://appuals.com/fix-uefi-firmware-settings-missing-in-windows-10/

There are 2 display ports on the 7010 did you try both?

Thanks. Read the article and disabled the fast startup following the instructions. Still nothing changed though.

I was considering doing Method 5. from the article where you create this shortcut, but not sure if this is a good idea. But then again, how bad can it be of course. Im going to try it as the next when I get around to it. 

By the way I replaced my CMOS battery with a fresh new one but that didn't help much either. 
I did it by resetting the CMOS in the process

• Unplugged the AC
• Take out old battery
• Hold the powerbutton for 10+ seconds
• Wait a couple of minutes (some instructions say just those 10 seconds)
• Put new battery in. 
• Plug AC back in 
• Fire up machine

Everything was still the same though. 

@speedstep I did try the other Displayport output quite early on, sorry forgot to mention this. I tried it again for good measure but no success alas. 

@redxps630 So I tried reporting a couple of times that I attempted the Method 5 from the article with no success either. Created the shortcut following the instructions but the only thing that happened was the popup window asking me for permissions for the Shutdown and Annotation tool. After clicking yes, computer is supposed to reboot now according to the article. But the only thing that happens is the popup disappears and Im back to the desktop. 

@redxps630 

Yes the keyboard does light up immediately each time I boot. 
I also finally gotten hold or a VGA screen. So the VGA screen responds well. I see the Dell splash screen, and I can get into the BIOS. Just for context I got this PC to see if what Linux would do and perhaps make a Hackintosh. Which is what made me install POP Os from a flash drive onto an SSD that I installed after I saw that I could change boot to UEFI in the computers BIOS. Despite relying on the VGA screen, I was happy to at least be able to have a boot meny where I could choose the SSD  

At this point Im not really sure if it's worth exploring how to make the Optiplex boot into the BIOS and/or bootscreen from the Displayport alone, which it still can't. I did however experiment with a couple of configurations to see what happens. 

First thing was see what happens when I boot while both screens connected. This got me back to the original situation where thing werent working. Screens remain black, no Dell splash screen and then all of a sudden the Windows boot screen is there. 

Then I disconntected the Mechanical drive that has Windows 10 installed, but the Linux SSD connected. Both monitors still connected. Result: VGA screen does light up but just blank dark grey. DP screen not at all. Also, led doesn't light up at all, i.e. not even flashing. 

Last thing so far was disconnecting the VGA screen and just turn on the PC with only the DP connected. I remember being surprised that it did boot into the Linux SSD. But I don't remember if I connected the HDD again before I did so. Which shouldn't have been a surprise if I did.

So now I'm really wondering if I should just get a cheap GPU that is hackintosh friendly and see what happens or if I should continue my battle to make the PC boot into the BIOS with only the DP connected. 
One thing that I should have mentioned is that after my attempts to reset the CMOS with the jumpers and all, I never saw that the date was reset. Did I just do it wrong all this time then?

Hi,

I have exactly the same problem with my optiplex 990.

It would be great if I would need to play with VGA to enter the BIOS 🤬.

I will try with some cable/adapter VGA->HDMI…