Side Loading a Non-Steam Game to a Steam Deck
Every time I want to add a Non-Steam Game to my Steam Deck I have to look up all the commands in my history and remember all the exact things I frequently forget to make it happen. This will never happen again.
We're using a Linux desktop PC here.
Mount the Deck to the Desktop
sudo sshfs "deck@$STEAMDECK_IP:/home/deck" /mnt/deckfs -o allow_other
You don't strictly need to sshfs into the deck. But it has a few benefits, including observability of the remote and local file systems.
You can make sure you're putting things in the right place. You have tab completion and can easily select a valid remote path.
Sync the Game Directory to the Deck
rsync -avz --progress "$GAME_DIRECTORY" "/mnt/deckfs/$GAME_DIRECTORY"
It is important that you use rsync, as the game files could be quite large and the transfer could take a while.
If the deck goes into sleep mode, it sometimes stops the transfer. With the rsync command you can continue an interrupted transfer.
On Windows Games with Linux
There is a scenario that comes up often.
On a Steam Deck, you're generally not running native Linux applications, although you could.
Typically you will have a Windows executable (exe). Steam knows what to do with that using it's Proton windows emulation.
However if the executable is a Setup file that installs the game rather than firing it up immediately, it can be quite difficult to figure out where Steam is installing the game. For this reason, if you have a Setup executable, you'll often want to fire it locally using wine. Wine will install the game in a more predictable location so that you can find it and send it over to the deck as described in the commands above.
Mounting an Install Disc on Linux
A final common scenario is that you will have either Setup or the Game executable but it will be stored in a disc image (iso)
You can mount this with sudo mount -o loop /path/to/game.iso /mnt/iso, and run wine to install, and sshfs/rsync to send.
Adding the Game to the Steamdeck Interface
When the transfer is finished, boot the Steamdeck into desktop mode and open your Steam Library.
In the bottom left corner you will see + Add a Game.
Use it to Add a Non-Steam Game. Browse to the newly transferred game exe.
Navigate to the game in the library and open its properties using the cog wheel. Select the Compatibility tab.
Check Force the use of a specific Steam Play compatibility tool and select Proton Experimental from the drop down.