I believe that Add PostGIS spatial functions to a custom schema other than "public" in PostgreSQL shouldn't have been closed because it's not a duplicate of Using schema other than public in PostGIS?
If anything, the first question is the opposite of the second question.
The second question is asking whether PostGIS features can be used with objects that themselves are not in the
public schema. The first question covers whether the PostGIS extension and its objects can be installed, themselves, into a schema other than
Should the "duplicate" be re-opened?