Linux mod.io fix

YOU CAN FIX IT MANUALLY (READ BELOW), in fact, this is what I would recommend. This mod is aimed at the people that are not comfortable with a terminal or people on handheld devices like the Steam Deck.

After the fix is applied, the mod can be uninstalled. 

What this does

The mod simply copies 3 files to another location. To do this manually, use these commands and restart core keeper:

mkdir -p "$HOME/.steam/steam/steamapps/common/Core Keeper/CoreKeeper_Data/MonoBleedingEdge/etc/mono/4.5"
cp "$HOME/.steam/steam/steamapps/common/Core Keeper/CoreKeeper_Data/StreamingAssets/Patcher/Linux/Core Keeper Patcher_Data/MonoBleedingEdge/etc/config" "$HOME/.steam/steam/steamapps/common/Core Keeper/CoreKeeper_Data/MonoBleedingEdge/etc/config"
cp "$HOME/.steam/steam/steamapps/common/Core Keeper/CoreKeeper_Data/StreamingAssets/Patcher/Windows/MonoBleedingEdge/etc/mono/4.5/machine.config" "$HOME/.steam/steam/steamapps/common/Core Keeper/CoreKeeper_Data/MonoBleedingEdge/etc/mono/4.5/machine.config"

Or if you're OK with running Core Keeper inside Proton, you can force the use of it in steam.

The more technical explanation:

For some reason, the files that the Mono runtime looks for when setting up http/https web request handlers is missing on the Linux core keeper installation.

This manifests itself as this error chain:

1. System.Net.WebRequest fails with NotSupportedException: The URI prefix is not recognized.
2. mod.io requests fail as HTTP ERROR [0 0] with WebRequest is null

n2 is what we see in the Player.log, but the cause is that Mono never loads webRequestModules due to the missing machine.config

Thankfully for us, Core Keeper ships a "Patcher" project that contains the exact files we need. By copying them to the path that mono expects, the mod.io networking stack gets properly initialized.