diff --git a/3rd-party/class.jetpack-amp-support.php b/3rd-party/class.jetpack-amp-support.php
index 9d798a3ec0ab3..27f22d1bf78ef 100644
--- a/3rd-party/class.jetpack-amp-support.php
+++ b/3rd-party/class.jetpack-amp-support.php
@@ -1,5 +1,4 @@
-<?php
-
+<?php //phpcs:ignore WordPress.Files.FileName.InvalidClassFileName
 /**
  * Manages compatibility with the amp-wp plugin
  *
@@ -7,7 +6,10 @@
  */
 class Jetpack_AMP_Support {
 
-	static function init() {
+	/**
+	 * Apply custom AMP changes onthe frontend.
+	 */
+	public static function init() {
 
 		// Add Stats tracking pixel on Jetpack sites when the Stats module is active.
 		if (
@@ -20,29 +22,43 @@ static function init() {
 		// Sharing.
 		add_filter( 'jetpack_sharing_display_markup', array( 'Jetpack_AMP_Support', 'render_sharing_html' ), 10, 2 );
 
-		// enforce freedom mode for videopress
+		// enforce freedom mode for videopress.
 		add_filter( 'videopress_shortcode_options', array( 'Jetpack_AMP_Support', 'videopress_enable_freedom_mode' ) );
 
-		// include Jetpack og tags when rendering native AMP head
+		// include Jetpack og tags when rendering native AMP head.
 		add_action( 'amp_post_template_head', array( 'Jetpack_AMP_Support', 'amp_post_jetpack_og_tags' ) );
 
-		// Post rendering changes for legacy AMP
+		// Post rendering changes for legacy AMP.
 		add_action( 'pre_amp_render_post', array( 'Jetpack_AMP_Support', 'amp_disable_the_content_filters' ) );
 
-		// Add post template metadata for legacy AMP
+		// Add post template metadata for legacy AMP.
 		add_filter( 'amp_post_template_metadata', array( 'Jetpack_AMP_Support', 'amp_post_template_metadata' ), 10, 2 );
 	}
 
-	static function admin_init() {
-		// disable Likes metabox for post editor if AMP canonical disabled
-		add_filter( 'post_flair_disable',  array( 'Jetpack_AMP_Support', 'is_amp_canonical' ), 99 );
+	/**
+	 * Apply custom AMP changes in wp-admin.
+	 */
+	public static function admin_init() {
+		// disable Likes metabox for post editor if AMP canonical disabled.
+		add_filter( 'post_flair_disable', array( 'Jetpack_AMP_Support', 'is_amp_canonical' ), 99 );
 	}
 
-	static function is_amp_canonical() {
+	/**
+	 * Is the page in AMP 'canonical mode'.
+	 * Used when themes register support for AMP with `add_theme_support( 'amp' )`.
+	 *
+	 * @return bool is_amp_canonical
+	 */
+	public static function is_amp_canonical() {
 		return function_exists( 'amp_is_canonical' ) && amp_is_canonical();
 	}
 
-	static function is_amp_request() {
+	/**
+	 * Does the page return AMP content.
+	 *
+	 * @return bool $is_amp_request Are we on am AMP view.
+	 */
+	public static function is_amp_request() {
 		$is_amp_request = ( function_exists( 'is_amp_endpoint' ) && is_amp_endpoint() );
 
 		/**
@@ -55,7 +71,10 @@ static function is_amp_request() {
 		return apply_filters( 'jetpack_is_amp_request', $is_amp_request );
 	}
 
-	static function amp_disable_the_content_filters() {
+	/**
+	 * Remove content filters added by Jetpack.
+	 */
+	public static function amp_disable_the_content_filters() {
 		if ( defined( 'IS_WPCOM' ) && IS_WPCOM ) {
 			add_filter( 'videopress_show_2015_player', '__return_true' );
 			add_filter( 'protected_embeds_use_form_post', '__return_false' );
@@ -71,7 +90,7 @@ static function amp_disable_the_content_filters() {
 	 *
 	 * @since 6.2.1
 	 */
-	static function add_stats_pixel() {
+	public static function add_stats_pixel() {
 		if ( ! has_action( 'wp_footer', 'stats_footer' ) ) {
 			return;
 		}
@@ -87,7 +106,7 @@ static function add_stats_pixel() {
 	 * @param WP_Post $post     Post.
 	 * @return array Modified metadata array.
 	 */
-	static function amp_post_template_metadata( $metadata, $post ) {
+	public static function amp_post_template_metadata( $metadata, $post ) {
 		if ( isset( $metadata['publisher'] ) && ! isset( $metadata['publisher']['logo'] ) ) {
 			$metadata = self::add_site_icon_to_metadata( $metadata );
 		}
@@ -105,10 +124,12 @@ static function amp_post_template_metadata( $metadata, $post ) {
 	 * @since 6.2.0
 	 *
 	 * @param array $metadata Metadata.
+	 *
 	 * @return array Metadata.
 	 */
-	static function add_site_icon_to_metadata( $metadata ) {
-		$size = 60;
+	private static function add_site_icon_to_metadata( $metadata ) {
+		$size          = 60;
+		$site_icon_url = class_exists( 'Jetpack_Sync_Functions' ) ? Jetpack_Sync_Functions::site_icon_url( $size ) : '';
 
 		if ( function_exists( 'blavatar_domain' ) ) {
 			$metadata['publisher']['logo'] = array(
@@ -117,7 +138,7 @@ static function add_site_icon_to_metadata( $metadata ) {
 				'width'  => $size,
 				'height' => $size,
 			);
-		} else if ( $site_icon_url = Jetpack_Sync_Functions::site_icon_url( $size ) ) {
+		} elseif ( $site_icon_url ) {
 			$metadata['publisher']['logo'] = array(
 				'@type'  => 'ImageObject',
 				'url'    => $site_icon_url,
@@ -138,23 +159,28 @@ static function add_site_icon_to_metadata( $metadata ) {
 	 * @param WP_Post $post     Post.
 	 * @return array Metadata.
 	 */
-	static function add_image_to_metadata( $metadata, $post ) {
-		$image = Jetpack_PostImages::get_image( $post->ID, array(
-			'fallback_to_avatars' => true,
-			'avatar_size'         => 200,
-			// AMP already attempts these.
-			'from_thumbnail'      => false,
-			'from_attachment'     => false,
-		) );
+	private static function add_image_to_metadata( $metadata, $post ) {
+		$image = Jetpack_PostImages::get_image(
+			$post->ID,
+			array(
+				'fallback_to_avatars' => true,
+				'avatar_size'         => 200,
+				// AMP already attempts these.
+				'from_thumbnail'      => false,
+				'from_attachment'     => false,
+			)
+		);
 
 		if ( empty( $image ) ) {
 			return self::add_fallback_image_to_metadata( $metadata );
 		}
 
 		if ( ! isset( $image['src_width'] ) ) {
-			$dimensions = self::extract_image_dimensions_from_getimagesize( array(
-				$image['src'] => false,
-			) );
+			$dimensions = self::extract_image_dimensions_from_getimagesize(
+				array(
+					$image['src'] => false,
+				)
+			);
 
 			if ( false !== $dimensions[ $image['src'] ] ) {
 				$image['src_width']  = $dimensions['width'];
@@ -184,7 +210,7 @@ static function add_image_to_metadata( $metadata, $post ) {
 	 * @param array $metadata Metadata.
 	 * @return array Metadata.
 	 */
-	static function add_fallback_image_to_metadata( $metadata ) {
+	private static function add_fallback_image_to_metadata( $metadata ) {
 		/** This filter is documented in functions.opengraph.php */
 		$default_image = apply_filters( 'jetpack_open_graph_image_default', 'https://wordpress.com/i/blank.jpg' );
 
@@ -198,8 +224,13 @@ static function add_fallback_image_to_metadata( $metadata ) {
 		return $metadata;
 	}
 
-	static function staticize_subdomain( $domain ) {
-		// deal with WPCOM vs Jetpack
+	/**
+	 * Return static WordPress.com domain to use to load resources from WordPress.com.
+	 *
+	 * @param string $domain Asset URL.
+	 */
+	private static function staticize_subdomain( $domain ) {
+		// deal with WPCOM vs Jetpack.
 		if ( function_exists( 'staticize_subdomain' ) ) {
 			return staticize_subdomain( $domain );
 		} else {
@@ -215,7 +246,7 @@ static function staticize_subdomain( $domain ) {
 	 * @param array $dimensions Dimensions.
 	 * @return array Dimensions.
 	 */
-	static function extract_image_dimensions_from_getimagesize( $dimensions ) {
+	private static function extract_image_dimensions_from_getimagesize( $dimensions ) {
 		if ( ! ( defined( 'IS_WPCOM' ) && IS_WPCOM && function_exists( 'require_lib' ) ) ) {
 			return $dimensions;
 		}
@@ -237,7 +268,10 @@ static function extract_image_dimensions_from_getimagesize( $dimensions ) {
 		return $dimensions;
 	}
 
-	static function amp_post_jetpack_og_tags() {
+	/**
+	 * Display Open Graph Meta tags in AMP views.
+	 */
+	public static function amp_post_jetpack_og_tags() {
 		if ( ! ( defined( 'IS_WPCOM' ) && IS_WPCOM ) ) {
 			Jetpack::init()->check_open_graph();
 		}
@@ -247,14 +281,25 @@ static function amp_post_jetpack_og_tags() {
 		}
 	}
 
-	static function videopress_enable_freedom_mode( $options ) {
+	/**
+	 * Force Freedom mode in VideoPress.
+	 *
+	 * @param array $options Array of VideoPress shortcode options.
+	 */
+	public static function videopress_enable_freedom_mode( $options ) {
 		if ( self::is_amp_request() ) {
 			$options['freedom'] = true;
 		}
 		return $options;
 	}
 
-	static function render_sharing_html( $markup, $sharing_enabled ) {
+	/**
+	 * Display custom markup for the sharing buttons when in an AMP view.
+	 *
+	 * @param string $markup          Content markup of the Jetpack sharing links.
+	 * @param array  $sharing_enabled Array of Sharing Services currently enabled.
+	 */
+	public static function render_sharing_html( $markup, $sharing_enabled ) {
 		if ( ! self::is_amp_request() ) {
 			return $markup;
 		}
@@ -264,23 +309,23 @@ static function render_sharing_html( $markup, $sharing_enabled ) {
 			return $markup;
 		}
 		$supported_services = array(
-			'facebook'      => array(
+			'facebook'  => array(
 				/** This filter is documented in modules/sharedaddy/sharing-sources.php */
 				'data-param-app_id' => apply_filters( 'jetpack_sharing_facebook_app_id', '249643311490' ),
 			),
-			'twitter'       => array(),
-			'pinterest'     => array(),
-			'whatsapp'      => array(),
-			'tumblr'        => array(),
-			'linkedin'      => array(),
+			'twitter'   => array(),
+			'pinterest' => array(),
+			'whatsapp'  => array(),
+			'tumblr'    => array(),
+			'linkedin'  => array(),
 		);
-		$sharing_links = array();
+		$sharing_links      = array();
 		foreach ( $sharing_enabled['visible'] as $id => $service ) {
 			if ( ! isset( $supported_services[ $id ] ) ) {
 				$sharing_links[] = "<!-- not supported: $id -->";
 				continue;
 			}
-			$args = array_merge(
+			$args         = array_merge(
 				array(
 					'type' => $id,
 				),
@@ -290,7 +335,7 @@ static function render_sharing_html( $markup, $sharing_enabled ) {
 			foreach ( $args as $key => $value ) {
 				$sharing_link .= sprintf( ' %s="%s"', sanitize_key( $key ), esc_attr( $value ) );
 			}
-			$sharing_link .= '></amp-social-share>';
+			$sharing_link   .= '></amp-social-share>';
 			$sharing_links[] = $sharing_link;
 		}
 		return preg_replace( '#(?<=<div class="sd-content">).+?(?=</div>)#s', implode( '', $sharing_links ), $markup );
diff --git a/bin/phpcs-whitelist.js b/bin/phpcs-whitelist.js
index f85a59fa88205..79124a81e1d76 100644
--- a/bin/phpcs-whitelist.js
+++ b/bin/phpcs-whitelist.js
@@ -1,6 +1,7 @@
 // If the file path starts with anything like in the array below, it should be linted.
 module.exports = [
 	'3rd-party/3rd-party.php',
+	'3rd-party/class.jetpack-amp-support.php',
 	'class.jetpack-gutenberg.php',
 	'class.jetpack-plan.php',
 	'extensions/',