I think this happened after Catalina.
sudo ls /Applications/Preview*
claims there is no such file, even though the file is perfectly visible in the Finder.
I have a script that relies on it:
function manp(){
man -t $1 | open -f -a /Applications/Preview.app
}
which I can fix by abbreviating to open -f -a Preview
but still ... where did Preview.app go?