I wanted to make a quick write-up for the steps I went through to get it working. Keep in mind that I am running the Epic Games version with Legendary and umu-launcher so a lot of these steps are extremely specific to umu-launcher and Legendary and will not translate to other versions. These steps will be almost identical for Heroic except these options will be in Heroic's GUI instead of in a config file. You should be able to extrapolate what to do with most of this info and apply it to other launchers but even so I'll try to help with any issues as best I can.
Let the game launch as normal to install Rockstar Launcher and dependencies if you already haven't.
To get GTA V working at all on with Epic Games, I created a batch file, called "fix.bat", that opens the launcher, then the game, then RAGEPluginHook:
start /B "null" PlayGTAV.exe %*
ping -n 15 localhost > nul
start /B "null" GTA5_BE.exe %* -useEpic -fromRGL
ping -n 15 localhost > nul
start /B "null" RAGEPluginHook.exe
exit
This file should be in the base game directory, where the GTA executable is.
Then I created a config file for Legendary (~/.config/legendary/config.ini) that changes the default executable to the file created in the previous step and sets some environment variables used by umu-launcher:
; GTAV config
[9d2d0eb64d5c44529cece33fe2a46482]
wrapper = mangohud gamemoderun umu-run
no_wine = true
override_exe = fix.bat
; GTA environment variables
[9d2d0eb64d5c44529cece33fe2a46482.env]
WINEDEBUG = -all ; stops wine spam in console after opening the game
WINEPREFIX = prefix ; can be wherever you want, this puts it in a folder called "prefix" in the game install directory
PROTONPATH = /usr/share/steam/compatibilitytools.d/proton-ge-custom ; pick a proton version you want to use, just put "GE-Proton" if you have no idea
STORE = egs
GAMEID = umu-271590
Then I installed the dependencies for RAGEPluginHook by using umu-launcher's ability to run winetricks verbs:
env WINEPREFIX=$HOME/Games/EpicGames/GTAV/prefix PROTONPATH=/usr/share/steam/compatibilitytools.d/proton-ge-custom GAMEID=umu-271590 STORE=egs umu-run winetricks dotnet472 vcrun2010 vcrun2015
This will probably take a while, just let it run.
Now install LSPDFR like you normally would into the base game folder where the GTA executable is located.
Launch the game like normal (legendary launch gtav) and (hopefully) everything will startup like normal with RPH running.
If you want to edit settings for RAGEPluginHook, you can run this command (change paths where required):
env WINEPREFIX=$HOME/Games/EpicGames/GTAV/prefix PROTONPATH=/usr/share/steam/compatibilitytools.d/proton-ge-custom GAMEID=umu-271590 STORE=egs umu-run $HOME/Games/EpicGames/GTAV/RAGEPluginHook.exe
and clicking the gear icon on the loader before the game starts.
First startup will most likely require that you enable the LSPDFR plugin in RPH settings before it actually loads.