postgresql-12-postgis-3 binary package in Ubuntu Focal riscv64

 PostGIS adds support for geographic objects to the PostgreSQL
 object-relational database. In effect, PostGIS "spatially enables"
 the PostgreSQL server, allowing it to be used as a backend spatial
 database for geographic information systems (GIS), much like ESRI's
 SDE or Oracle's Spatial extension. PostGIS follows the OpenGIS
 "Simple Features Specification for SQL".
 .
 To create the PostGIS extensions in a PostgreSQL 12 database, the
 postgresql-12-postgis-3-scripts package must be installed as well.

Source package