Error in Sanitizer.php

I get this error with WP 5.5.3 and the latest version of the plugin:

Un errore di E_ERROR è stato causato nella linea 96 del file /var/www/html/wp-content/plugins/safe-svg/lib/vendor/enshrined/svg-sanitize/src/Sanitizer.php. Messaggio di errore: Uncaught Error: Class 'DOMDocument' not found in /var/www/html/wp-content/plugins/safe-svg/lib/vendor/enshrined/svg-sanitize/src/Sanitizer.php:96
Stack trace:
#0 /var/www/html/wp-content/plugins/safe-svg/lib/vendor/enshrined/svg-sanitize/src/Sanitizer.php(200): enshrined\svgSanitize\Sanitizer->resetInternal()
#1 /var/www/html/wp-content/plugins/safe-svg/safe-svg.php(142): enshrined\svgSanitize\Sanitizer->sanitize()
#2 /var/www/html/wp-content/plugins/safe-svg/safe-svg.php(107): safe_svg->sanitize()
#3 /var/www/html/wp-includes/class-wp-hook.php(287): safe_svg->check_for_svg()
#4 /var/www/html/wp-includes/plugin.php(206): WP_Hook->apply_filters()
#5 /var/www/html/wp-admin/includes/file.php(754): apply_filters()
#6 /var/www/html/wp-admin/includes/file.php(987): _wp_handle_upload()
#7 /var/www/html/wp-admin/includes/media.php(301): wp_handle_upload()
#8 /var/www/html/wp-admin/async-upload.php(94): media_handle_upload()
#9 {main}
  thrown