UPDATE:
MacOS REALLY hates when you install anything unapproved by Apple via Developer ID, so it will LIE TO YOUR FACE. use xattr on pretty much any ‘corrupted’ dmg file to fix it.
EDIT:
you need some special tag with xattr look it up or smth
EDIT 2:
god this post is too many pings for anyone following this thread but use xattr -c FILENAME specifically