Enable the CRB and EPEL repositories, then add the official PostgreSQL YUM repositroy:

dnf install 'dnf-command(config-manager)' -y
dnf config-manager --set-enabled crb
dnf install -y epel-release
dnf install -y https://download.postgresql.org/pub/repos/yum/reporpms/EL-9-x86_64/pgdg-redhat-repo-latest.noarch.rpm

Disable the built-in PostgreSQL module to avoid conflicts:

dnf -qy module disable postgresql

List available versoins of PostgreSQL 12 and PostGIS 3.0 for PostgreSQL 12:

dnf list postgresql12 --showduplicates | sort -r
dnf list postgis30_12 --showduplicates | sort -r

Install specific versions of PostgreSQL 12 and PostGIS:

dnf install -y \
  postgresql12-12.9-2PGDG.rhel9 \
  postgresql12-libs-12.9-2PGDG.rhel9 \
  postgresql12-server-12.9-2PGDG.rhel9 \
  postgresql12-contrib-12.9-2PGDG.rhel9 \
  postgis30_12-3.0.5-1.rhel9

Initialize the database cluster:

/usr/pgsql-12/bin/postgresql-12-setup initdb

Adjust PostgreSQL configuration files:

In /var/lib/pgsql/12/data/postgresql.conf, set:

listen_addresses = '*'

In /var/lib/pgsql/12/data/pg_hba.conf, append:

host    all             all             0.0.0.0/0               md5

Start and enable the PostgreSQL service:

systemctl enable --now postgresql-12

Perform initial database setup as the postgres user:

su - postgres

# Create a new user
createuser appuser

# Set password for the user
psql -c "ALTER USER appuser WITH PASSWORD 'securepass';"

# Create a database owned by the new user
createdb geodb -O appuser

Verify connectivity and explore the database:

# Connect remotely (replace IP accordingly)
psql -h 10.10.10.10 -d geodb -U appuser

# List users
psql -c "SELECT usename FROM pg_user;"

# List databases
psql -l

# Restore from SQL dump
psql -d geodb -U postgres -f dump.sql

# Interactive session
psql geodb
geodb=> \du   -- list roles
geodb=> \dt   -- list tables
geodb=> \q    -- quit

# Drop database if needed
dropdb geodb