Can you recommend a free light-weight MySQL GUI for Linux?

You can use phpMyAdmin, since it is one of the best free tools. This can be used for every system with PHP and MySQL. It is a free and open source administration tool for MySQL and MariaDB. PHPMYADMIN

Here is the URL to download −

https://www.phpmyadmin.net/downloads/

The following are the features of phpMyAdmin −

• Open source tool
• MySQL and MariaDB database management.
• One of the most popular MySQL administration tools
• Easily Import data from CSV and SQL
• Export data to various formats. These include : CSV, SQL, XML, PDF, Word, Excel, LaTeX, etc.
• Administering multiple servers

You can also use EMMA. This is also a light-weight application.