DBD::mysql::st execute failed: Access denied for user 'rt_admin'@'localhost' to database 'rt5'

I am following the installation manual from this website: ManualInstallation - Request Tracker Wiki

In the installation steps, I am configuring MySQL.
In the SETUP RT’S DATABASE step, after I run the command:
I got the following error:

In order to create or update your RT database, this script needs to connect to your mysql instance on localhost (port '') as rt_admin

Please specify that user's database password below. If the user has no database

password, just press return.

Password:

Working with:

Type: mysql

Host: localhost

Port:

Name: rt5

User: rt_user

DBA: rt_admin

Now creating a mysql database rt5 for RT.

Done.

Now populating database schema.

Done.

Now inserting database ACLs.

[warning]: DBD::mysql::st execute failed: Access denied for user ‘rt_admin’@‘localhost’ to database ‘rt5’ at /opt/rt5/sbin/…/lib/RT/Handle.pm line 475. (/opt/rt5/sbin/…/lib/RT/Handle.pm:475)

[critical]: DBD::mysql::st execute failed: Access denied for user ‘rt_admin’@‘localhost’ to database ‘rt5’ at /opt/rt5/sbin/…/lib/RT/Handle.pm line 475. (/opt/rt5/sbin/…/lib/RT.pm:409)

DBD::mysql::st execute failed: Access denied for user 'rt_admin'@'localhost' to database 'rt5' at /opt/rt5/sbin/../lib/RT/Handle.pm line 475.

I have passed the point of make fixdep; all CPAN modules necessary to get RT5 working are installed. I have set the password in the RT_SiteConfig.pm file as for the Admin user of the Database when creating it at its installation but the issue persists.

I really appreciate any help here.

Can you access the “rt5” database as the rt_admin user in the MySQL shell? My guess is the database user rights aren’t quite enough

Yes, I can access it using rt_admin. I used the same password for rt_admin and root user and their authentication_string is the same in mysql.user.

Can rt_admin alter the database?

yes! I tried every way inside the DB to make it possible and it all works through MySQL shell but apparently not from apache.

What do the db logs say?

I have the following:

[Note] Server socket created on IP: ‘127.0.0.1’.
[Note] Event Scheduler: Loaded 0 events
[Note] /usr/sbin/mysqld: ready for connections.

Version: ‘5.7.36-0ubuntu0.18.04.1’ socket: ‘/var/run/mysqld/mysqld.sock’ port: 3306 (Ubuntu)
[Note] Aborted connection 11 to db: ‘rt5’ user: ‘rt_user’ host: ‘localhost’ (Got an error reading communication packets)