Issues #3444231 and #3453060: EmbeddedEnforceForm: build own buttons:

Since we're no longer extending ConfigFormBase, we don't have a
arent::buildForm() to call, so we have to build the form actions.

src/Form/EmbeddedEnforceForm.php

@@ -35,16 +35,16 @@ class EmbeddedEnforceForm extends AbstractEnforceForm {
 
     $this->addConfigFormInfo();
 
-    /** @var \Drupal\Core\Form\FormInterface */
-    $form = parent::buildForm($this->form(), $this->formState());
-
-    // Move the submit buttons into our container.
-    $form['config_enforce']['actions'] = $form['actions'];
-    unset($form['actions']);
-
-    $form['config_enforce']['actions']['submit']['#value'] = $this->t(
-      'Save enforced configuration settings'
-    );
+    $form['config_enforce']['actions'] = [
+      '#type' => 'actions',
+      'submit'  => [
+        '#type'   => 'submit',
+        '#button_type'  => 'primary',
+        '#value' => $this->t(
+          'Save enforced configuration settings'
+        )
+      ],
+    ];
 
     $form = $this->buildFormThemeSettings($form);