This is a lightweight plugin that changes the default confirmation behavior for forms that "redirect". The plugin will add an interstitial message and push a structured dataLayer event to Google Tag Manager containing any fields with a name property.

// Assuming a submission from gravity form ID 4 on www.level.agency
{
  event: 'lvl.form_submit',
  form: {
    id: 'gravity-forms:0-4', // 0 is the site ID (will be 0 if not using multi-site)
    name: 'Contact Us', // The human readable form name
    provider: 'wordpress:www.level.agency',
    field_values: {
      entry_id: 343, // Reference ID to gravity form entry.
      // key: value pairs of all $entry data that can be tied to a field w/ a `name`
    }
  }
}

Any field you wish to access in the field_values that isn't entry meta needs to have a value in the Advanced Field Settings "Allow field to be populated dynamically" Parameter Name setting. The value placed here will be used as the property name in the form.field_values object.

By default, the event pushed to the dataLayer is prefixed with a lvl. namespace. This can be customized using the lvl:gravityforms/gtm/event_namespace filter:

add_filter('lvl:gravityforms/gtm/event_namespace', function($namespace) {
  return 'custom_namespace';
}, 10, 2);

By default, the redirect delay is set at 1500 milliseconds. This can be configured using the lvl:gravityforms/gtm/redirect_delay filter:

add_filter('lvl:gravityforms/gtm/redirect_delay', function($delay) {
  // Change the delay to 1000ms
  return 1000;
}, 10, 2);

By default, the redirect interstitial content is set to We are processing your submission. Please wait.... This can be configured using the lvl:gravityforms/gtm/redirect_interstitial_content filter:

add_filter('lvl:gravityforms/gtm/redirect_interstitial_content', function($content) {
  return "Please wait, we're processing your request.";
}, 10, 2);

The plugin uses CSS animations and variables for the spinner inside the interstitial. The default spinner color is #000 but it can be customized via: lvl:gravityforms/gtm/redirect_spinner_color.

add_filter('lvl:gravityforms/gtm/redirect_spinner_color', function($color) {
  // Changes spinner to LVL Pink
  return '#FD6EF8';
}, 10, 2);