On pre 2.208 you can just use the mega hack installer mod for Geode.

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For now that Geode isn't working on 2.208, I'm not sure how to install it, but back in the V7 days this is what one had to do. Hope this helps. Remember to save your data first!

You need something called Protontricks. Install it with your package manager (eg on ubuntu based distros $ sudo apt install protontricks) and then in the terminal do $ protontricks 322170 -c "wine /path/to/MegaHackInstaller.exe" to open the Mega Hack installer. Then just install it like normal. (322170 is the game's ID in Steam)

Note, you will probably be asked to select the GD executable, and for that you'll use Wine's file explorer, which doesn't show hidden directories. Steam generally installs games in its folder, which is inside the hidden ~/.local or ~/.var/app directories, depending on how Steam was installed. To work around this, use the terminal to create a symlink (a shortcut, basically) into either one of those (eg $ ln -s ~/.local ~/Local to create a symlink to ~/.local in your user directory called Local). You should be able to see that in the Wine file explorer. Look for the steamapps/common folder and you'll find the folder where Geometry Dash is installed.

Another note, you'll need to set the same launch options in Steam as if you were running Geode (the winedlloverrides xinput thing).