Here's how to downgrade to 2.206 on Steam to use Geode

[shadow basin]

(I copied this from arcticwoof but I just changed the manifest lol. also added additional instructions for Linux and macOS)

1. Press WIN + R on your desktop to open the run menu, then type steam://nav/console or open a browser and paste steam://nav/console in the address bar (latter is easiest method for macOS, Linux, etc)
2. in the console, paste this: download_depot 322170 322171 7903404280228366327
   2b. if on macOS: download_depot 322170 322172 6862317728889446455
3. Wait for it to complete, This could take a few minutes
4. navigate to C:\Program Files (x86)\Steam\steamapps\content and go into the depot_322171 folder, this contains all the game files, basically just the gd folder but with a different name.
   4b. if you're on macOS, in Finder, go the top-right bar: Go --> Go to Folder --> ~/Library/Application Support/Steam/steamapps/content (atleast i think it's there).
   4c. on Linux it's most likely in ~/.steam/steam/steamapps/content
5. Once you are in the folder with the game files, create a text file called steam_appid, open it, and type 322170, and then save.
6. Install Geode and BE SURE TO CHANGE THE INSTALL DIRECTORY TO THE DEPOT FOLDER
7. After Geode is installed, You are now done and can open the game.
8. (optional) If you want to transfer your existing mods from the latest version, drag and drop the folders **DON'T INCLUDE DLLs/EXE IN THE LATEST VERSION, JUST THE FOLDERS ** from the 2.207 GD version into the depot_322171 folder (2.206). Be sure to drag and drop geode folder into the downgraded version. You can also drag other folders for other mods.

If you want more info/video on how to downgrade, Read this post by Moldy

[shadow basin]

mobile is a different process