The old WordPress host reported that image rotation was unsupported. The recorded fix installed PHP’s GD extension and restarted the matching PHP-FPM service:
$ sudo apt install php-gd
$ sudo service php7.2-fpm restart
The php7.2-fpm name belongs to that earlier environment. Match an extension to the PHP runtime actually serving the site, rather than assuming the CLI PHP and web PHP use the same configuration.
This is a historical dependency note. No package was installed or service restarted for this revision.