We'd love to distribute a Mac version of Blankspace, unfortunately Apple's latest changes to MacOS make it very awkward to run non-notarized code (potentially leading to support nightmares for us, as we're not Mac based). Notarizing code requires a $99/year Apple Developer Licence and regrettably it's hard as a small indie developer to justify that sort of cost.
You should be able to play using the Windows version of the game by following the instructions at the bottom of https://patreon.renpy.org/macos-notarization.html though - just be sure to test using the demo version first to check if it works for you fine.