Solved Oxide won't start with the new "start-example" (Oxide not installed)

You don't have Oxide installed. Make sure you overwrote all files with the ones from the zip you downloaded, and that you didn't run SteamCMD to validate/update after. The example is just a standard Rust server example, not specific to Oxide.

 

You may have files there, but the RustDedicated_Data/Managed/Assembly-CSharp.dll is most likely vanilla. Oxide is a mod, and that is where the magic happens.