and yes, after running (in a terminal) **sudo mkdir /Library/Foo; sudo chown mylogin /Library/Foo ** and then setting the Derived Data folder in Xcode's Settings > Locations > Derived Data to /Library/Foo the app builds just fine for MacOs "Designed for iPad" (which is Catalyst, yes?) [This issue has bedeviled me for MONTHS, and happened way before 13-14-15 of Xcode]

see below