In this guide I'm going to show you how to mod Fallout 4 on steam deck with Vortex

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!

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 4'' 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/fallout4/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 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'' and ''loadorder.txt''

Now go to our document folder on Steam Deck:
/home/deck/.local/share/Steam/steamapps/compatdata/377160/pfx/drive_c/users/steamuser/AppData/Local/Fallout4/
And paste/overwrite the ''Plugins.txt'' and ''loadorder.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

Go to:
/home/deck/.local/share/Steam/steamapps/compatdata/377160/pfx/drive_c/users/steamuser/Documents/My Games/Fallout4
And open Fallout.ini.
Now Scroll to Archive and edit to say:
[Archive]
sResourceIndexFileList=Fallout4 - Textures1.ba2, Fallout4 - Textures2.ba2, Fallout4 - Textures3.ba2, Fallout4 - Textures4.ba2, Fallout4 - Textures5.ba2, Fallout4 - Textures6.ba2, Fallout4 - Textures7.ba2, Fallout4 - Textures8.ba2, Fallout4 - Textures9.ba2
sResourceStartUpArchiveList=Fallout4 - Startup.ba2, Fallout4 - Shaders.ba2, Fallout4 - Interface.ba2
SResourceArchiveList=Fallout4 - Voices.ba2, Fallout4 - Meshes.ba2, Fallout4 - MeshesExtra.ba2, Fallout4 - Misc.ba2, Fallout4 - Sounds.ba2, Fallout4 - Materials.ba2
SResourceArchiveList2=Fallout4 - Animations.ba2
sResourceDataDirsFinal=
SGeometryPackageList=Fallout4 - Geometry.csg
SCellResourceIndexFileList=Fallout4.cdx
SResourceArchiveMemoryCacheList= Fallout4 - Misc.ba2, Fallout4 - Shaders.ba2, Fallout4 - Interface.ba2, Fallout4 - Materials.ba2
bInvalidateOlderFiles=1

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

Two 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)

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3498442654