Hey, sorry for that!
I've just tested a fix with 2 different macs and it should be fixed now, please let me know if that works for you!
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Edit: Indeed, this seems to be caused by a Unity bug when signing macOS builds.
I manually made some changes to bypass their signature, but the game now asks for a security check before opening it the first time (System Preferences -> Security & Privacy)… Annoying, but at least it seems to run now.
I'll keep an eye on this.