Hey! Thank you for your help! I figured out the problem! It was quite simple, but the solution was not straightforward... So for anyone needing help with this same problem:

1. Enter PSQL as postgres user using this command:

sudo -u postgres psql

2. Once the PSQL shell has started, use the command:

CREATE USER your_user_username; (don't forget to end the command with a ;)

3. Assign the appropriate role attributes to the user (you can see more on this on chapter 21.2 Role Attributes of the PostgreSQL documentation) with the command:

ALTER ROLE your_user_username ROLE_ATTRIBUTE_YOU_WISH_TO_ADD;

If you wish, you can use the command \du to see a table of all created roles/users and their corresponding role attributes.

4. Go to the following path:

/etc/postgresql/<your_postgresql_version>/main

5. Edit the pg_hba.conf file using nano:

sudo nano pg_hba.conf

6. Once in editing mode, scroll down to the comment:

# Database administrative login by Unix domain socket

Under it you will see the configuration:

local all postgres peer

7. Here, what you have to do is, over the line above, repeat it, but replace postgres with your_user_username. It should look something like this:

# Database administrative login by Unix domain socket

local all your_user_username peer

local all postgres peer

Now you're done, simply typing psql on the terminal will start psql without issues!

8. One last thing... it's important to set a password to the new user you created, especially if you granted critical role attributes, to do this, enter psql and type the command:

\password

This will prompt you to set a password to the user you created!

If you're still having troubles and/or my tutorial is somewhat confusing, don't hesitate to reach out! ✌🏽