It worked when I manually downloaded + made executable. I usually install via the desktop app to have automatic updates but I expect you won't be making updates as frequently as games do so it should be all right. Thanks!
I'm using the itch.io desktop app and it says "No manager for installer unknown". In the stack trace it says "no mapping for file extension .86_64". I'm running Pop!OS 64-bit:
$ lspcu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit