Hello [NAME] , Bradthetechnut brought up the driver issue and indeed, that was the main problem.  Your HP monitor is using DisplayLink driver technology and graphics driver is required.  You installed graphics driver on your hdd/ssd but not in BIOS, therefore, no graphics signals at boot until OS is loaded. To see your BIOS, you need to change your monitor to other portable models which have USB as power and HDMI/VGA for graphics signals.
I have a Dell OptiPlex 7050, and I bought an HP EliteDisplay S140u for the monitor. This is the only monitor I intend to use. It's a highspeed USB3 connection, not an HDMI connection. The monitor works great, once the computer boots up. However, I can't get to the BIOS on this monitor, or see the booting process. I know the computer can access USB immediately, because my USB keyboard is available on boot. I have seen questions like this, but they always refer to Dell laptops. Someone will have a cracked screen, and they'll need access to their USB external monitor at boot. The answer is usually to hold fn+f2 at boot, or to boot with the laptop lid closed. Obviously the lid is irrelevant for my desktop, and fn+f2 didn't work. Does anyone know how I can get my monitor going at boot?
Dell OptiPlex 7050 Micro: USB portable monitor at boot