An error occurred while saving the commentHubert commented
I'm glad I did not pay money for something as broken as Twitch )when it comes to installing games).
I tried hacking my custom path into the installation "form". That is pretty simple since the Twitch desktop app is simple a modified Chrome browser. But it did not take my custom path and instead installed the game in the very default location (which I had deleted in the "form").
You can still copy or move the installed game from wherever Twitch installs it, and launch the game without that stupid Twitch desktop app :D