If you have lightsail instance, it is super easy to connect to mariadb (or mysql) installed with bitnami.
First take the password by cating
cat bitnami_application_password
Then connect
mysql --host localhost --user root --port 3306 -p
The above command could be deprecated, use with mariadb
/opt/bitnami/mariadb/bin/mariadb --host localhost --user root --port 3306 -p
You dont need phpmyadmin. This is the rightway to avoid error cannot connect to socket.