BTW I installed itch and installed the game from the app
and used nemo to manage the files
I first installed linux beta, the typed sudo apt update then sudo apt upgrade then sudo apt install nemo. Then Copy the Karlson to linux files then extract the files from nemo. Also go in this link chrome://flags/#exo-pointer-lock once you see it click default next to pointer lock for linux applications then click enable.
I hope this helps