Is it just my Mac because I keep getting an exclamation that “Doppelgänger” cannot be opened because the developer cannot be verified." .. ? it won't open up :(
Hi!! I use mac and have a similar issue, so putting this here for anyone else who may need help:
It worked for me after I dragged it to my Dock bar and right clicked to open from there. Alternatively, I've seen some people just open it from Finder instead. There seems to be a general issue with itch.io games on Mac in general, so if that doesn't work, you can try and find some forums for better help perhaps
Hope that helps!! <3 <3