Issue #3381912: Add default MailSystem config for Symfony Mailer Lite emails

symfony_mailer_lite.install

+<?php
+
+/**
+ * Implements hook_install().
+ */
+function symfony_mailer_lite_install() {
+  $settings = Drupal::configFactory()->getEditable('mailsystem.settings');
+  $settings->set('modules.symfony_mailer_lite.none', [
+    'formatter' => 'symfony_mailer_lite',
+    'sender' => 'symfony_mailer_lite',
+  ])->save();
+}