It seems that the current Linux version 4.3.0.1948 requires Steam to be installed to be able to play the game, as the game is crashing with the following output:
gamer@pegasus6:/usr/local/games$ LANG=C ./launch [S_API] SteamAPI_Init(): SteamAPI_IsSteamRunning() did not locate a running instance of Steam.
dlopen failed trying to load:
/home/gamer/.steam/sdk64/steamclient.so
with error:
/home/gamer/.steam/sdk64/steamclient.so: cannot open shared object file: No such file or directory
[S_API] SteamAPI_Init(): Sys_LoadModule failed to load: /home/gamer/.steam/sdk64/steamclient.so
terminating with uncaught exception of type Inanity::Exception*
./launch: line 9: 3416 Aborted LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./x64 ./x64/insatia
I guess that's not supposed to happen with the itch version :-)