Just a quick look at FS 22 running on my new Steam Deck 256 GB Model. I copied all of my mods over from my main Windows gaming PC. once you have them copied to a flash drive, or w/e copy them over to the Steam Deck in Desktop Mode, the default folder for them is
HERE: /home/deck/.local/share/Steam/steamapps/compatdata/1248130/pfx/drive_c/users/steamuser/Documents/My Games/FarmingSimulator2022/mods
Once they are in the mod folder launch the game and Boom all your mods are gtg.
ALSO : To get my controller working correctly I had to launch FS 22 while in Desktop mode, it recognized a controller and now working in normal Deck mode.