I've tried to troubleshoot my problem some more. By launching AppGameKit, trough steam, via terminal command
"steam -applaunch 325180".
Below is, i believe, the lines from where steam tries to launch it, until failure.
Steam_SetMinidumpSteamID: Caching Steam ID: 76561197968630995 [API loaded no]
GameAction [AppID 325180, ActionID 2] : LaunchApp changed task to Starting with ""
GameAction [AppID 325180, ActionID 2] : LaunchApp changed task to SiteLicenseSeatCheckout with ""
GameAction [AppID 325180, ActionID 2] : LaunchApp changed task to CreatingProcess with ""
GameAction [AppID 325180, ActionID 2] : LaunchApp waiting for user response to CreatingProcess ""
GameAction[AppID 325180, ActionID 2] : LaunchApp continues with user response "CreatingProcess"
Opted-in Controller Mask: 0
Game update: AppID 325180 "App Game Kit", ProcID 12280, IP 0.0.0.0:0
Loaded Config for Local Override Path for App ID 325180: /home/MYUSERNAME/.local/share/Steam//controller_base/empty.vdf
[325180]Non-Steam Controller Configs Enabled: 1
Loaded Config for Local Override Path for App ID 325180: /home/MYUSERNAME/.local/share/Steam//controller_base/empty.vdf
>>> Adding process 12280 for game ID 325180
GameAction [AppID 325180, ActionID 2] : LaunchApp changed task to WaitingGameWindow with ""
GameAction [AppID 325180, ActionID 2] : LaunchApp changed task to Completed with ""
/home/MYUSERNAME/.local/share/Steam/steamapps/common/App Game Kit 2/Tier1/Editor/bin/geany64: symbol lookup error: /home/MYUSERNAME/.local/share/Steam/steamapps/common/App Game Kit 2/Tier1/Editor/bin/geany64: undefined symbol: g_type_check_instance_is_fundamentally_a
Game removed: AppID 325180 "App Game Kit", ProcID 12280
[0930/153105.289987:ERROR:web_plugin_impl.cc(38)] Widevine registration is not supported after context initialization