i got it working on the mac (m1 air) using these commands in terminal:
cd /Users/MYUSERNAME/Downloads/Stacklands_v1.0.5\ \(macOS\)
(you can replace the thing after cd with wherever the .app is located in your filesystem... the easiest way is to type 'cd' and then drag the containing folder itself into terminal, it'll copy the path right in)
chmod a+x Stacklands.app/Contents/MacOS/Stacklands
xattr -cr Stacklands.app