Hello in the 1.16.5 version in the config file we could disable the flux recipe enableFluxRecipe = false
In the 1.18.2 config file I don't see this line.
How can I disable the default flux dust recipe?

It's in server config, you can find it in save folder, e.g. .minecraft/saves/New World/serverconfig/fluxnetworks-server.toml
If you want to change it for all singleplayer worlds you create, copy it to .minecraft/defaultconfigs/fluxnetworks-server.toml and make your changes there.

The server configs will be synchronized to the client when joining a server, so the client can see these changes between servers. But the configs in the config folder cannot be synchronized.

Thanks you :)