If you have ever had a problem to login to phpmyadmin with root you will need to add the rights.
login to mariadb/mysql:

mysql -uroot -p

check if user is added:

SELECT User, Host FROM mysql.user WHERE Host <> 'localhost';Code language: HTML, XML (xml)

MariaDB [(none)]> SELECT User, Host FROM mysql.user WHERE Host <> 'localhost';Code language: HTML, XML (xml)

+----------+------+
| User | Host |
+----------+------+
| librenms | % |
+----------+------+

Now add the root user:

GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY 'YOUR PASSWORD' WITH GRANT OPTION;Code language: JavaScript (javascript)

And now flush:

flush privileges;

MariaDB [(none)]> SELECT User, Host FROM mysql.user WHERE Host <> 'localhost';Code language: HTML, XML (xml)

+----------+-------------+
| User | Host |
+----------+-------------+
| librenms | % |
| root | % |
+----------+-------------+