SQuirreL SQL Client is a GUI that allows you to view the structure of a JDBC compliant database, browse the data in tables, issue SQL commands etc. Supports MySQL, PostgreSQL, MariaDB, and SQLite.

SQuirreL SQL Client is a graphical Java program (GUI) that will allow you to view the structure of a JDBC compliant database, browse the data in tables, issue SQL commands etc.
The Flatpak version currently includes drivers for MySQL, PostgreSQL, MariaDB, Actian Avalanche, Apache Derby, H2, HSQLDB, Microsoft MSSQL, Sybase, Mckoi, and SQLite.