Operative guide. See https://stackoverflow.com/questions/4629796/issues-installing-postgis

Issues installing PostGIS

# postgresql
sudo apt install postgresql-11
sudo apt install postgresql-server-dev-11

# dependencies
sudo apt install libxml2-dev
sudo apt install libgeos-dev
sudo apt install libproj-dev
sudo apt install libgdal-dev

# postgis
wget http://postgis.net/stuff/postgis-3.1.0dev.tar.gz
tar xvfz postgis-3.1.0dev.tar.gz
cd postgis-3.1.0dev
./configure
make
make install