Step 1: Press the three keys simultaneously – Alt + Ctrl + Del and reach the "shut down" option. Step 2: Select the drop-down menu with the "tab" key and use arrow keys to select "restart." This will restart the system, and probably the black screen issue disappears.  
I have recently purchased a used Optiplex 3060 and went to install Windows 10 V21H2 (not the latest) from a USB I have used in the past, indeed 2 USB devices. On booting the USB the screen displayed a series of Arcs along the bottom of the monitor.  I stopped the process, concerned that there may be a video issue, but booting a XPE windows version showed no Arc.  I also booted a few other Linux devices with no issue, but to do so had to disable Secure Boot.  I usually do this first when building PCs, but did not in this case. At this point I learned that disabling Secure Boot removed the Arcs.  I was able to replicate this on another 3060. Is this related to Secure Boot, the particular install I used or something else.  Google did not help, but note sure what to call this.  I am most interested to confirm it's not a hardware issue, though I think that I can replicate the issue on another device rules that out. Any thoughts? [IMAGE] The arcs disappeared at the first install screen and the OS installed as normal.  I do not see the arcs when booting the PC.
Video Display Issue Installing Windows 10