@DanielMcColgan seems to be /opt/homebrew-cask/Caskroomby default using brew cask. And inside i can see the ndm folder indeed. Then obviously the app gets unpacked inside /Applications/ndm.app
Also i get a warning Warning: The default Caskroom location has moved to /usr/local/Caskroom. brew asking me to change the location i don't know why, but if you don't have that warning probably the app gets installed here /usr/local/Caskroom.