vlans-compare - A LibreNMS plugin package that shows the difference between lists of vlans on devices or ports.
Go to the LibreNMS root directory and run the following command as the librenms user.
./lnms plugin:add dmbokhan/vlans-compare
php artisan vendor:publish # and choose Dmbokhan\VlansCompare\Providers\VlansCompareServiceProvider
php artisan route:clear
Head to the web browser and go to Overview - Plugins - Vlans Compare. There are multiple-option select fields where you can choose your devices or ports (using Ctrl + Click) to see differences between their vlans on the plugin page.