Public code repos are not anonymous

They can be. Throwaway account on hosted git service, connected through anonymity service (TOR, VPN…).

And torrents require some form of advertising

Many indexers are anonymous, a magnet link on a forum or even a site like lemmy is good enough.

I’m not going to argue about the semantics of anonymity on the internet. If you want to stay hidden enough to distribute a mod and not be found out who you are, you can do it. Its not that difficult.