I do have a discrete GPU in the laptop. BTW I read somewhere that the iGPU might have to be turned on through the BIOS. Is that true and how do I do that?
No. That is typically a desktop feature of the motherboard; generally not available in laptops as they typically need the on-board graphics in order to save battery power. Unless you went into BIOS yourself and disabled them, you don't need to go back in and re-enable them.
Well even if they did switch to the iGPU, wouldn't that be a reason to have it shown in the Device Manager?
As already mentioned, unless you have a Windows 10 driver installed for your specific iGPU, it won't show up in device manager. Since a Windows 10 driver for your specific iGPU does not exist, Windows 10 supplies a Generic driver for your iGPU which allows it to function at it's most base level.
You're bellyaching about nothing. You got Windows 10 installed and running on your laptop that doesn't support WIndows 10. Very much like Microsoft dropped support for Windows 7, HP dropped support for your laptop. Be happy about it and move on!
-Wolf sends
P.S. and about that username...