CentOS 8.4 release notes says they fixed that issue in that release,
after having resolved it in CentOS Stream 8.
    https://wiki.centos.org/Manuals/ReleaseNotes/CentOS8.2105#Fully_Functional_Boot_ISO

I suggest reporting the problem to bugs.rocky.org.

Dave

On Tue, Jun 22, 2021 at 01:51:11PM -0500, Jon Pruente wrote:
> On Tue, Jun 22, 2021 at 12:34 PM Teh, Kenneth M. <
> [log in to unmask]> wrote:
> 
> > I tried the boot iso but it does not have a built-in list of mirrors. I'm
> > stuck at the installation source.  I need a url, either a specific repo or
> > a url.  Please post if anyone knows one.
> >
> 
> I had the same problem with the boot ISO. I used the minimal ISO to install
> a VM with a plain base system with DHCP networking and
> automatic partitioning. After rebooting into the installed OS everything
> seemed fine. I refreshed repo data, installed epel-release, refreshed
> again, then installed some basic tools from BaseOS and EPEL. For an
> initial install it was fine.
> 
> ISTR it was CentOS that had a similar missing repo URL problem with their
> first 8 release.