After downloading the linux version, I accidentally selected Deutsch, and I'm unable to find a way to change it back to English... Tried reinstalling it without any luck, as well as looking into the settings, won't let me change anything.

Help?

You can select the game's language by editing the lang file located in the $HOME/.local/share/freebirdgames/tothemoon/ directory. If you selected German, it must contain "de". Just change it to "en" and you're good to go.

Alternatively, you can delete said directory and you'll be prompted again to select the language the next time you run the game.