From what I was able to figure out, the bug was already fixed for CentOS by adding this block:
<% if rhel_compatible && @host.operatingsystem.name.downcase.include?("centos") && os_major >= 8 && medium[:url] && medium[:url].include?("AppStream") -%>
<% appstream_present = true -%>
# renamed from "<%= medium[:url] %>" for CentOS Anaconda to work
repo --name AppStream --baseurl <%= medium[:url] %>
<% else -%>
repo --name <%= medium[:name] %> --baseurl <%= medium[:url] %> <%= medium[:install] ? ' --install' : '' %><%= proxy_string %>
<% end -%>
<% end -%>
<% if rhel_compatible && @host.operatingsystem.name.downcase.include?("centos") && os_major >= 8 && medium_uri && medium_uri.to_s.include?("BaseOS") && !appstream_present -%>
# repository added using BaseOS to AppStream string replacement
repo --name AppStream --baseurl <%= medium_uri.to_s.gsub("BaseOS", "AppStream") %>
<% end -%>
But it only matches CentOS and not the derivatives that use the same repo structure. But as how the rhel_compatible variable already sorts out which derivatives are using the same repo structure, I removed matching CentOS specifically here:
<% if rhel_compatible && os_major >= 8 && medium[:url] && medium[:url].include?("AppStream") -%>
<% appstream_present = true -%>
# renamed from "<%= medium[:url] %>" for CentOS Anaconda to work
repo --name AppStream --baseurl <%= medium[:url] %>
<% else -%>
repo --name <%= medium[:name] %> --baseurl <%= medium[:url] %> <%= medium[:install] ? ' --install' : '' %><%= proxy_string %>
<% end -%>
<% end -%>
<% if rhel_compatible && os_major >= 8 && medium_uri && medium_uri.to_s.include?("BaseOS") && !appstream_present -%>
# repository added using BaseOS to AppStream string replacement
repo --name AppStream --baseurl <%= medium_uri.to_s.gsub("BaseOS", "AppStream") %>
<% end -%>
And that did fix the kickstarting issues in my environment 