I am trying to connect LibreOffice Base with an MySQL database, in phpMyAdmin, with a JDBC-connection.
The first step is to select which database you want to select:
If you're using Red Hat like linux distros like Fedora, you can install it from the repositories with yum or dnf and then:
In Base goto Tools/Options/Java, click Classpath and select /usr/share/java/mysql-connector-java.jar in the file browser.
https://fedoraproject.org/wiki/QA:Testcase_MySQL_or_MariaDB_in_libreoffice-base