Many thanks to chieftex and saber_breaker88 on reddit for the post here. This gist just adds some more notes and updates to those instructions, this was followed successfully on 2021-09-03, some steps have been removed (e.g. with flatseal) since they were not needed at that point.
The instructions below seem quite long, but they don't actually take that long to run - about half the time is just getting CEP set up on Windows so we can copy the files over, the whole thing should be doable in half an hour to an hour.
- On Windows, install P4G and go through the whole process of applying the mods you want, following instructions on p4g.cep.one. When this is complete, you should be able to run Persona with the mods successfully. We'll use the files from here on the Steam Deck.
- Back on Steam Deck, go to desktop mode (press steam button, go down to power, press desktop mode)
- Once in desktop mode, load discover (this is already installed on your steam deck). To load it, either click icon on the bar at the bottom, or use the bottom left button (on Windows this would be the Start button), click system, then discover.
- In the search button at the top, type "protontricks". When it appears in the right column, click "install" on it.
- Still on the steam deck, open a browser and go to "Download and Prepare" on p4g.cep.one
- Scroll to the bottom, and you will see a few links. Download the first two files (the ones that start with "Visual c++") and the fourth one "NET 5 Desktop Runtime". Note, when you click this last one, a new page will open. You want to download both the "x86" and "x64" versions of the runtime, shown by the blue arrows in this image
- You now want to locate these four files you downloaded. One way is to open your browser downloads (I used chrome on the steam deck for this) and click "show in folder" which will open Dolphin (a file browser). Another way is to open dolphin directly (bottom left button, then system, and it'll be in there), and go to "Downloads".
- Now, locate the first of the four files you downloaded, and RIGHT-click on it. Choose "Open with Proton tricks". This may fail with a message about not having access to a device, if you're using an SD card - if so, follow the instructions given to run a command in a terminal (click the bottom left "start" button, then type "terminal" and run the suggested Konsole app). You will then get a prompt for which environment to run in - select "Persona 4 Golden" from the list. You will run other appications with proton tricks, in each case select Persona from the list.
- When the installer runs correctly, a window will appear after a few seconds, asking to install the file. If there is a checkbox to agree, check it, then click install and proceed.
- Repeat these steps for each of the four files you downloaded.
- Time to copy things from the windows PC to the steam deck. I recommend Warpinator for this. You need to install Warpinator on steam deck from the Discover store like other apps above, and then Winpinator (the equivalent) on the windows pc. I won't go into how to use that here, there are other guides on this sub or on Google though.
- TIP: Once you've installed Winpinator (the windows version), open it, click File -> Preferences, click the "Connection" tab, and then in the "Network interface to use" drop down, pick the device you use to access your network (it'll be your internal wifi or your ethernet adapter for most people). Don't leave it set to Automatic. I've just saved you minutes or hours of your life with this one tip - you're welcome!
- Send the ".ReloadedII" folder from your windows PC to the steam deck (if you followed the instructions on p4g.cep.one you will have made a "Mods" folder - ".ReloadedII" is inside the persona mods folder on your Windows PC).
- Once you've sent the folder over, you can click the little folder icon in warpinator on the deck, to view the location of the files. This will open Dolphin (from before) - if the folder doesn't open, you can run Dolphin yourself from the bottom bar, it's the folder icon, and then navigate to Home -> Warpinator. But wait! Where is the folder you sent over? You're sure you sent it right! Yes, don't worry :) This folder starts with a full stop (aka period) "." which means it's hidden. To see hidden files in dolphin, click the options (burger) button in the top right, then choose "show hidden files". If you don't have an options button, it may be under a menu, otherwise you may have to google to find it.
- Great, now we can see the folder, we can move it. Right click on the folder and choose copy (or cut so we don't have to go back and delete it later). We now want to move it to the folder in which P4G is actually installed. In dolphin: Click Home -> .steam -> steam -> steamapps -> common -> Persona 4 Golden. Now you are in the game folder, right click in some blank space and choose to "paste one folder".
- Go into the ".ReloadedII" folder you just pasted, and find the "reloadedII.exe" (NOT the reloadedII32.exe). Right click on this, and choose to open with protontricks. Welcome to Reloaded! If it wants you to update, ignore it. Instead, go to your windows pc, update it there, then copy that new folder over as per the above point. Now, click skip tutorial, and you'll be at the main screen.
- Click the button that looks like face with a yellow background on the left. Choose "edit application".
- Now, you want to fill in the second line here (path to p4g.exe). How do you get this easily? Minimise Reloaded, and load Steam - there should be a shortcut to steam on your desktop background. When Steam loads, find Persona 4, click it, and choose the cog icon on the right to get to its settings. Click manage, then "browse local files". This will put you back in Dolphin. Look familiar?! Ok, now you're in the game folder, find "P4G.exe" here. RIGHT-click it and choose "Copy Location". I think you know where we're going next:
- Go back to Reloaded, and delete everything in that second line (the location of the application) so it's blank (don't click update). Once you've deleted everything, RIGHT-click on the line and choose "paste". Bam! Or, if it doesn't work, unfortunately you might have to just paste the location into a text file then type it out in the text box. When you've got the path in there one way or another, click "Update" and you should see a file dialog with "P4G.exe" in it - select this and it should fill out the text box with a path starting with a letter, e.g. "Z:".
- One more thing to do in Reloaded - in the same window, scroll to the boom and click "advanced tools & options". Then click the button that says "Deploy ASI Loader". Say OK to the prompt.
- Now back to windows, where as a result of installing the mods Aemulus will have created a mods folder under your steam "Persona 4 Golden" folder. This is important as the guide says - make sure you are looking at the correct mods folder!
- Now, using warpinator from before, send this folder to your steam deck. Once it's on the deck, copy that folder, as we're going to paste it in two places. The first is Home -> .steam -> steam -> steamapps -> common -> Persona 4 Golden. Paste one in here. NOTE: don't paste the Mods folder inside the Mods folder if there's one already - just paste what's inside that folder. You don't want to end up with a folder called Mods\Mods. The second place to paste it is Home -> .steam -> steam -> steamapps -> common -> Persona 4 Golden -> Scripts.
- Well done for getting this far - this is the final step! Go back to game mode (use the icon on the desktop). Then run P4G from steam as normal! You should notice that it loads Reloaded now, and that Reloaded runs a bunch of scripts to load the mods. If it doesn't get that far, double check you got the path to the game right (path to p4g.exe above). If it gets that far and then just loads Persona 4 without giving you grief, you probably put the Mods folder in the wrong place(s).
- The app may crash several times before running (although for me it ran first time - might be improvements to Proton?) - just try re-running until it works.
Hey there — having trouble this this step
“When the installer runs correctly, a window will appear after a few seconds, asking to install the file. If there is a checkbox to agree, check it, then click install and proceed.”
Attached is what happens when I install with protontricks. Not sure what to do here (sorry for potato cam)