Note:
I'm not responsible for any issues with the Steam Deck, if you do any modding on the Steam Deck it will be your own responsibility! YOU HAVE BEEN WARNED!

I ONLY RECOMMEND DOING THIS IF YOU KNOW WHAT YOU ARE DOING, DON'T DELETE ANYTHING YOU DON'T KNOW!

In this guide I'm showing you how to install, use and mod with Vortex on the Steam Deck for Fallout New Vegas.
You will need 2 things:
Vortex account, Go to ''https://www.nexusmods.com/'' and create a free account.
A Steam Deck (Ofcourse)

I recommend installing the game on your internal drive, just in case.

Go to https://github.com/pikdum/steam-deck/ and scroll to installation section.
Copy by clicking the double square symbol:
Open the ''Konsole'' on the Steam Deck and paste/enter
It will run for a little and then add an Vortex application to your Desktop.
Double click it and let it run for a while to install it.
Now open the program and in vortex go to the tab games on the left side and search for the game ''Fallout New Vegas'' and click on manage, Vortex will then ask you to tell it where the game is installed on your system and might want you to restart the program.
To find where the game is located you need to use one of the following folders depending on where you installed the game:
J: to internal games
K: to sd card games
Now go to the setting menu, sub group mods and click on suggested and apply.
it should now say in the the line: J:Vortex Mods\{game} or K:Vortex Mods\{game}
When that is done, reopen Vortex and Login on the right top side.
When done, minimize it.
Now Vortex is ready to use.

Now go to the Nexus website: https://www.nexusmods.com/games/newvegas/mods.
Find yourself a mod you like and click on it, it will open the mod page and show you a description, some pictures.

When you find a mod you like, click on files, click on mod manager download and then slow download.
It will give you popup asking if you allow it to download it to vortex, it will also give you the option to auto allow it.
When you download it, it will maximize Vortex and start downloading the file in it.
When done go to the tab mods and click on the blue button to install the file.
Then enable the mod and now you are ready to play with the mod installed.

Now for essential mods:
https://www.nexusmods.com/newvegas/mods/70801 Improved Console (NVSE)
https://www.nexusmods.com/newvegas/mods/65906 Console Paste Support
https://www.nexusmods.com/newvegas/mods/77415 ROOGNVSE Plugin
https://www.nexusmods.com/newvegas/mods/58277 JIP LN NVSE Plugin
https://www.nexusmods.com/newvegas/mods/66927 JohnnyGuitar NVSE
https://www.nexusmods.com/newvegas/mods/72541 ShowOff xNVSE Plugin
https://www.nexusmods.com/newvegas/mods/66537 NVTF - New Vegas Tick Fix
https://www.nexusmods.com/newvegas/mods/66347 lStewieAl's Tweaks and Engine Fixes
https://www.nexusmods.com/newvegas/mods/80993 lStewieAl's Engine Optimizations
https://www.nexusmods.com/newvegas/mods/71973 Combat Lag Fix (NVSE)
https://www.nexusmods.com/newvegas/mods/84823 VATS Lag Fix
https://www.nexusmods.com/newvegas/mods/80666 ActorCause Save Bloat Fix
https://www.nexusmods.com/newvegas/mods/71336 kNVSE Animation Plugin
https://www.nexusmods.com/newvegas/mods/57174 UIO - User Interface Organizer
https://www.nexusmods.com/newvegas/mods/68714 FNV Mod Limit Fix

This mod is not needed to play, but extremely recommended.
https://www.nexusmods.com/newvegas/mods/62552?tab=description 4GB patcher

The 4GB patcher can only be installed manually, so go to the files tab and download first ''4GB Patcher'' manual, and then slow download.
When the download is done, extract it and move the FNVpatch to your fallout new vegas root folder.
If you don't know how to find it, go to your steam library and go to Fallout New vegas, then click on the cog on the right, go to files and then browse local files.
When you have the FNVpatch in your root folder, double click it and a batch file will open, give it a couple seconds to patch and it then will tell you to press any button to close the batch file.

Now the game is from 2GB patched to 4GB, if you use texture mods, this will make it less likely to crash the game (Try to use as many 1K textures where possible)

Now that we have all our mods installed, we need to have the mods load into the game.
Vortex doesn't seem to move the esp. doc to the correct folder, so we have to do this manual.
Go to Vortex, click on open, click Open Game Application Data Folder and copy ''Plugins.txt''

Now go to our document folder on Steam Deck:
/home/deck/.local/share/Steam/steamapps/compatdata/22380/pfx/drive_c/users/steamuser/AppData/Local/FalloutNV/
And paste/overwrite the ''Plugins.txt''

The Github says that post-deploy shortcuts should work as well, but seem hit or miss to me.
These are added on your desktop as well when you installed the Vortex launcher.
For Fallout 3/4/new vegas and skyrim

Download fallout 3 archive invalidation manual version (it works for fallout nv too) You can find the FO3 version here- http://fallout3.nexusmods.com/download/37379

Download the manual version. Extract and move the archieveinvalidationinvalidated.bsa to your Fallout New Vegas data folder.

Then look for your Fallout.ini Falloutprefs and fallout_default.ini files. The Fallout.ini File and Falloutprefs will be in Your documents folder under `My Games` (where your saves folder is) and your Fallout_default.ini in your Fallout New Vegas folder where your FalloutNV.exe is. Open them both up. Scroll down and look for for [Archive] Make sure you paste this in all three the Ini.files such as Fallout_Default And Fallout.ini and Falloutprefs.

change it so it looks like this:

[ARCHIVE]
SInvalidationFile=
iRetainFilenameOffsetTable=1
iRetainFilenameStringTable=1
iRetainDirectoryStringTable=1
bCheckRuntimeCollisions=0
bInvalidateOlderFiles=1
bUseArchives=1
SArchiveList=Fallout - Voices1.bsa, Fallout - Sound.bsa, Fallout - Misc.bsa, ArchiveInvalidationInvalidated!.bsa, Fallout - Textures.bsa, Fallout - Textures2.bsa, Fallout - Meshes.bsa

You can just start the game from your library if you have installed 4GB.
It will auto load the script extender.

Three IMPORTANT Notes:
1. make sure to see if a mod needs a requirement, on the description page it will tell you if and what is needed for the mod to work, it will then also give you the links to the mods.
2. make sure you check the amount of plugins you are using, you can see it in Vortex under the tab plugins and then look in the top right where it says active.
Your max is 255 plugins, not every mod will add plugins (Usually texture mods don't, but mods that add content do)
3. It is highly recommended to use 1K texture mods, the game has a 2GB cache and with the 4GB patcher will double that cache.
when this cache goes over the 2GB or 4GB it will crash the game, textures will fill this cache up fast.

https://cs2bus.com/sharedfiles/filedetails/?id=3498442654