Add currecnt languge slug of WPML to media url in activity stream.

functions.php

<?php
/**
 * Add this code snippet to theme's functions.php
 *
 * Add currecnt languge slug of WPML to media url in activity stream.
 *
 */
if ( ! function_exists( 'rtmedia_wpml_activity_urls' ) ) {
	function rtmedia_wpml_activity_urls( $permalink, $media, $id ) {
		global $sitepress;

		// Get media ids array.
		$medias = ( isset( $_POST['rtMedia_attached_files'] ) && ! empty( $_POST['rtMedia_attached_files'] ) ) ? $_POST['rtMedia_attached_files'] : array();

		// Get current language.
		$lang_slug = ( isset( $_GET['lang'] ) && ! empty( $_GET['lang'] ) ) ? sanitize_text_field( wp_unslash( $_GET['lang'] ) ) : '';
		if ( ! empty( $lang_slug ) && isset( $_POST['action'] ) && 'post_update' === $_POST['action'] && ! empty( $medias ) && $sitepress->get_default_language() !== $lang_slug ) {
			$link = site_url();
			// replace site url with current language slug.
			$permalink = str_replace( $link, $link . '/' . $lang_slug, $permalink );
		}
		return $permalink;
	}
}
add_filter( 'get_rtmedia_permalink', 'rtmedia_wpml_activity_urls', 99, 3 );