Registering an Embed handler for posts from Telegram (t.me)

Add code in your file function.php

Tested:
WordPress 6.4.2 (Classic Editor/Gutenberg Editor)
PHP 7.4

/**
 * Embed register handler from Telegram post (t.me).
 *
 * @since    1.0.0
 */
add_action( 'init', 'wphaf_embed_register_handler_telegram' );

function wphaf_embed_register_handler_telegram() {
  wp_embed_register_handler(
    'telegram',
    '~https://t\.me/([a-z0-9_-]+)/([0-9]+)+~im',
    'wphaf_callback_embed_handler_telegram'
  );
}

/**
 * Callback function embed register handler from Telegram post (t.me).
 *
 * @since    1.0.0
 */
function wphaf_callback_embed_handler_telegram( $matches ) {
  return '<script async src="https://telegram.org/js/telegram-widget.js?21" data-telegram-post="' . $matches[1] . '/' . $matches[2] . '" data-width="100%"></script>';
}