This method uses Offline Mode to launch any game except for Family Shared games (and free trials/free weekend games, probably). No appmanifest editing or console usage required*!

1. Setting up Offline Mode:
   
   1. Make sure you logged in with Remember my password ticked beforehand
      
   2. Go to Steam > Settings, and under Account tab, ensure that Don't save account credentials on this computer is not selected
      
   3. Exit Steam with Steam > Exit
      
   4. Open the Steam > config > loginusers.vdf file in a text editor
      

      Default Steam paths:

      • Windows:
        
        C:\Program Files (x86)\Steam
      • Linux:
        
        ~/.local/share/Steam

   5. Under the desired user, set "SkipOfflineModeWarning" to "1"
      
2. Make a copy of your Steam shortcut, or make a batch/shell script with the path to steam.exe (Windows) or simply steam (Linux)
   
3. In target field/the launch command, append:
   
   "+@AllowSkipGameUpdate 1 +dont_touch_this"

   Examples:

   • Windows:
     
     "C:\Program Files (x86)\Steam\steam.exe" "+@AllowSkipGameUpdate 1 +dont_touch_this"
   • Linux:
     
     steam "+@AllowSkipGameUpdate 1 +dont_touch_this"

4. Optionally make the shortcut/script run on startup according to the procedure for your OS/setup
   
5. Launch Steam with that shortcut/script
   
6. Go to Steam > Settings, and under Interface tab, verify that Run Steam when my computer starts is not selected

Important: Never launch games you don't want updated outside of Offline Mode!

If you keep Steam open:

1. Switch to Offline Mode with Steam > Go Offline... > Enter Offline Mode
   
2. Enter Small Mode with View > Small Mode (unless your client is older than the arrival of Chromium-based library)
   
3. Launch the game
   
4. If you want/need Steam networking: Switch back with Steam > Go Online... and continue playing

If you only launch Steam when needed:

1. Edit the Steam shortcut/script from earlier
   
2. In target field/the launch command, append:
   
   -offlinemode steam://open/minigameslist
   Optionally, if you want Steam to truly be offline, add**:
   
   -net_fake_state NoSteam
   If you want to make shortcuts/scripts for each game individually, instead use:
   
   -offlinemode -applaunch <AppID>

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*A much faster method is setting internal ConVar @AllowSkipGameUpdate to 1, as outlined later. Using Offline Mode ensures that no updates are started by the client.
**This was added around May 2022, so it requires a fairly recent client version.