On Ubuntu, to connect:

sudo -u postgres psql

then

create user john createdb;

or

create user john;
alter user john createdb;

create with password

create user bobbins;
alter user bobbins createdb;
alter user bobbins password 'snuffle';

schema privileges

CREATE DATABASE EXAMPLE_DB;
CREATE USER EXAMPLE_USER WITH ENCRYPTED PASSWORD 'Sup3rS3cret';
GRANT ALL PRIVILEGES ON DATABASE EXAMPLE_DB TO EXAMPLE_USER;
\c EXAMPLE_DB postgres
# You are now connected to database "EXAMPLE_DB" as user "postgres".
GRANT ALL ON SCHEMA public TO EXAMPLE_USER;

Allow Remote

Source: this stackoverflow

In postgresql.conf

listen_addresses = '*' # allow all

and in pg_hba.conf

host    all             all             192.168.1.1/24           scram-sha-256

the systemctl restart (not just reload) the postgresql service.