@kuhtopf I glanced at that and it seems odd. (oh yes, it's eight years old -- it was for installing the Windows version through Wine, Absolutely obsolete unless you are trying to make a retro system...)
Now I'm not sure if there are tricks for a Chromebook, but you should have a file named "stardew_valley(something).sh"
Look at the properties. It should have "executable" ticked (I don't remember if it came like that).
Then just click it and follow the directions, to install the game.
Or open a console, go to the directory (folder) the file is in, type ./Stardew_...sh (type ./St and then hit tab,)
I haven't been using a Chromebook but I'm a dedicated Linux-user since 1995 or something...