I have the Linux x64 version that runs fine with an internet connection

Overload
v1.0.1880
24685
en-US

This is what I get without an internet connection:

Running Overload
chmod: changing permissions of ‘/usr/local/share/Overload/game//Overload.x86’: Operation not permitted
chmod: changing permissions of ‘/usr/local/share/Overload/game//Overload.x86_64’: Operation not permitted
chmod: cannot access ‘/usr/local/share/Overload/game//RunDedicatedServer.sh’: No such file or directory
Set current directory to /usr/local/share/Overload/game
Found path: /usr/local/share/Overload/game/Overload.x86_64
Mono path[0] = '/usr/local/share/Overload/game/Overload_Data/Managed'
Mono config path = '/usr/local/share/Overload/game/Overload_Data/Mono/etc'
Preloaded 'ScreenSelector.so'
Preloaded 'libCSteamworks.so'
Preloaded 'libopenvr_api.so'
Preloaded 'libsteam_api.so'
Unable to preload the following plugins:
libUnetEncryption.so
ScreenSelector.so
libCSteamworks.so
libsteam_api.so
Logging to /home/charlie/.config/unity3d/Revival/Overload/Player.log
[S_API FAIL] SteamAPI_Init() failed; SteamAPI_IsSteamRunning() failed.
[S_API FAIL] SteamAPI_Init() failed; unable to locate a running instance of Steam, or a local steamclient.so.

I surely hope this isn't how it is supposed to work. I don't buy any games from steam for this very reason.

Please let me know what I can do to fix this
Thanks

Edit with more info:

The game runs fine if I unplug the ethernet cable so it can't be trying to "phone home" It works fine if I turn the modem off. However if I turn off the router then it hangs at the very end of the loading process. I use a dedicated Linux PC for a router if that matters any.

So it isn't that much of a problem but I wonder what could be causing that?

Something to do with the multiplayer function perhaps?