It should be assigned automatically when launching Unwell for the first time based on your system's default language. You can always change the language later in the main menu settings.
I remember the first time I launched a game in Polish as a kid. Back then, finding a game with a Polish localization was... a rarity.
Today, it's a little surreal to realize that we've created a Polish version of our own game.
— Head Protege
Seek shelter and resources. Craft tools, traps, and fortifications.
Pray that you survive the next cycles of the Well.
No two are ever the same...
When the Well falls silent, solve puzzles with no single correct solution.
Find your way deeper.
And remember:
The Great Dig was a lie.