Aurora R7, how to automatically start when power is on?

Hello,

I will not have access to the power button of my Alienware Aurora R7 once I place it in the cabinet I bought it for, and I need a solution to boot it.
I was initially thinking of having a button switch in the cabinet with wires going to a "power" jumper" on the mother board but I haven't been able to find it, would anyone be able to point me to it  on the attached picture or any pictures of the motherboard ?  (I found pics of the motherboard here : https://www.amazon.com/Alienware-Aurora-LGA1151-Motherboard-IPCFL-SC/dp/B07W988YW2  )

An alternative I thought of is having the PC boot automatically when powered up, as the cabinet will be powered off most of the time and I will plug it into the power outlet when I need to use it. Unfortunately despite trying different options in the R7 Bios (AC recovery power on, autopower on for "every day"...) nothing worked, the PC doesn't automatically start when plugged into the power outlet.

Any other thoughts or suggestions most welcome ! Thanks !