When installing the itch app on Linux, itch-setup copies itself to ~/.itch/itch-setup - normally it's being run from another location, so the copy works fine, but if it's already being run from ~/.itch/itch-setup, it's probably opening itself for writing (which truncates the file) and reading (which is now reading a 0-length file), which results in a broken installation.
See https://itch.io/post/566021
When installing the itch app on Linux, itch-setup copies itself to ~/.itch/itch-setup - normally it's being run from another location, so the copy works fine, but if it's already being run from ~/.itch/itch-setup, it's probably opening itself for writing (which truncates the file) and reading (which is now reading a 0-length file), which results in a broken installation.