GTA V Heroic specific guide

Download prerequisites (Wine-GE)

GTA V's Multiplayer only runs with Wine-GE, a custom version of Wine made by GloriousEggroll. Download the latest version here (Note: Check twice if the upmost version on this page is actually the newest one. Sometimes GE releases specific version for specific games, you don't want those here).
Once downloaded, extract the contents to ~/.config/heroic/tools/wine/. The folder should look something like this:

Create a new Wineprefix for the game

A Wineprefix is sort-of like a small Windows installation. Depending on the game you want to run, you might need special programs installed, which in turn could break other games. This is why I'd recommend to create a seperate Wineprefix for any game that doesn't work with default settings (like this one).

1. Create a new folder, ideally in a location that is easy to remember (I use ~/Wine/Prefixes/). This will be a central spot for all your Wineprefixes.
2. Create a folder inside your central folder. The name is again up to you, I prefer gta-v
3. Open up a Terminal, and run the following command:
   export WINEPREFIX=$HOME/Wine/Prefixes/gta-v (adjust this path if you changed them in steps 1 and 2)
   What this will do: This will tell Wine that it should target this folder as its prefix.
   Important: Unless stated otherwise, run every command in this same Terminal. If you accidentally close it, re-do the steps from here!
4. Run export PATH=$HOME/.config/heroic/tools/wine/wine-ge-6.20-1-x86_64/bin/:$PATH.
   If your Wine-GE version is named differently (once 6.21 comes out), adjust the name accordingly. Just make sure to not forget the /bin/:$PATH at the end!
   What this will do: This will expand your PATH variable (which is the variable your Terminal looks at to know what programs to run) with the path to your custom Wine version. By putting it at the start like this, the terminal will prioritize the Wine-GE version.
5. Run wine --version to make sure the last command was successful. You should see either wine-4.11-...-... (Staging) or the actual version number with -GE- somewhere in it (some Wine-GE versions have the one Version string, some have the other)
6. Run wineboot --init && wineserver --wait. This will, as you can probably guess, initialize the Wineprefix and wait for initialization to finish.

Phew, finally done with that command line stuff. From now on, no more Terminal work is required. Feel free to close the Terminal you have open.

Configuring Heroic

Open up Heroic, hover over GTA V and click the gear icon. This should bring you to the game-specific settings.

1. Set your WinePrefix folder: Click the folder icon and navigate to ~/Wine/Prefixes/gta-v
2. Select your Wine Version: Click the dropdown, then select the correct version (it'll have the same name as the folder in ~/.config/heroic/tools/wine/)
3. Enable the "Auto Install/Update DXVK on Prefix" toggle

Actually playing the game

Well, that took long enough. Let's play the game already!

When pressing "Play now" in Heroic, after a bit of initialization work, the Rockstar Games Launcher installer pops up. Select your language (Note: I'm not sure if the language selected influences any of the steps in here, I've only tested with English), accept the EULA & ToS and whatnot, and accept the license agreement. In the installation location step, I'd recommend to not change the install location (not sure if this causes issues, but I'd rather not find out). Disable the desktop shortcut checkbox, it won't work (and Heroic offers the option to create better shortcuts anyways).
After some more waiting, you'll get this error:

Oh no, did you do something wrong? Well, no. This error is actually completely normal and, as far as I know, even happens on Windows! Just click "OK", then launch the game again.

This time, the Rockstar Games Launcher will actually launch up and update itself and then install Social Club. Once that's done, you'll finally get a login prompt. Enter your login details (don't worry, you're not insane, keystrokes are a bit delayed) and enable "Remember me" and "Auto sign in".
After more waiting, you'll end up in this screen:

(which is for some reason very dark right now; Halloween edition? Anyways)
You'll see here that GTA V is marked as "Buy now". At this point, you'll need another close (you might even have to kill the "Launcher.exe" process through your Task Manager). Starting the game again, you'll get a "Cloud Save" message. From testing, I don't think this message actually does anything, as GTA V will save-sync either way. But just in case, click "Enable Cloud Saves"/"Not right now" depending on your preference.
After this, the game will launch like normal and you can finally play