Seconding this. And as another lemming said, moving a working setup from a Windows system can make your life easier. But once you have MO2 running, most mods can just be installed in it like normal. Though SteamOS makes it more trouble than its with to auto download mods via mod manager. Easier just to use the manual download option and then manually install it.

Also, there is a Linux specific version of the 4GB patch. You have to make it executable and run it in the terminal to actually get it to patch.

You can run things like the BSA decompressor using proton tricks.

Or you can just run the 4GB patch and the BSA decompressor on a windows install and then copy the whole FNV folder over to your deck (overwriting files). That works too.

If you are a TTW kind of guy, do that on Windows, making it an installable mod, and then just copy that over. And do it before the BSA decompressor, or you will need to make a clean install of FNV.

Honestly, if you install MO2 using the link Headbangerd17 linked above, you can pretty much just follow the Viva New Vegas gude. Just use protontricks for the BSA decompressor and the Ultimate ESM fixes things, and the linux specific 4gb patch. Or again, do all of it on Windows and copy over the game folder and the MO2 folder.