Modding on a Steam Deck and Linux

This method has been confirmed to work on Risk of Rain 2, ROUNDS, and Enter the Gungeon, and should work for all unity games. For this tutorial Enter the Gungeon will be used to show the steps, but the steps will be more or less the same for any other unity game.

First Steps

The Steam Deck will need to be in Desktop Mode

First, you will need to download r2modman, either from the Thunderstore or the AppImage release from github Launch it and find the game you are trying to mod. IF YOU GET THIS POPUP, IGNORE IT AND CLICK CONTINUE

After that, you should be greeted with this screen Go to the online tab and install whatever mods you like, the mod manager will automatically download any dependencies required for mods you download.

The Hard Part

Once you have your mods installed, go to the settings tab, highlighted in this image: Once there, click the Browse Profile Folder option in the All tab. Your file manager should open to a screen like this

Leave the file manager open and open your steam library, and navigate to the game you are modding. To the left of the Play button, there will be a Gear icon. Click the gear icon, scroll down to Properties, and click Compatibility. Check the Box labelled "Force the use of a specific Steam Play compatibility tool", then select Proton 7.0-5 from the drop down list. Steam will have to download the Windows version of the game. Once the download is finished, go to the Local Files tab in the game properties window and select Browse. This should open the game directory in a new file manager tab.Your File manager should look like this.

Go to the File Manager tab that was opened earlier to the mod profile, and copy everything in the folder, then paste all of it in the game directory. Your game directory should now look like this

Go back to Steam and reopen the Game Properties window, and select the general tab. In the Launch Options text box, type or paste WINEDLLOVERRIDES="winhttp.dll=n,b" %command% If all steps have been done correctly, you should now be able to launch the game through Steam in Desktop Mode or Game Mode and have your mods load too.

Final Notes

There are a few notable limitations of this method, mainly that r2modman does not work in Game Mode, meaning that any time a mod need to be updated, you will have to switch back to desktop mode, relaunch r2modman, download whatever updates, then copy the plugins folder from the profile into the game directory.