I am having the same issue. I formatted the USB as fat32, and created the usb with the Rufus application.
I have tried setting the specific url instructed here (Installation Source error). I also tried the url of the iso itself. (…\iso\Rocky-8.4-x86_64-dvd1.iso). I have had a second person to verify there are no typos in my url. I also tried using the mirror at pulsant.com .
This is a fresh install on a Dell Poweredge T410. There is no other OS on the system. I have confirmed that I have network access.
Based on no response from trunglv, i am hoping that means his last idea worked. I am about to try it as well, and will update with the results.