How to proxy RockBox Utility to localhost?

[Darthagnon]

I work without internet quite a bit. I would like to use RockBox Utility without depending on an internet connection to access the server. I have replicated the most recent release files available from https://download.rockbox.org/ and am serving the files and folders on localhost with an http server. How do I tell RockBox Utility to look there, rather than online? I have tried the proxy settings and Charles Proxy to rewrite queries, but it always fails.