Telegram founder Pavel Durov says Apple has prevented global updates since April 2018. He claims the issue began when Russia blocked Telegram and demanded Apple delete it from the App Store. Without updates, the app won’t work on the latest version of iOS and does not comply with the European General Data Protection Regulation. Russia only makes up 7% of all Telegram users, but the app is still available on Apple’s App Store but hasn’t been able to deliver technical updates to installed versions anywhere in the world.”]
Source: https://www.darkreading.com/application-security/telegram-apple-has-blocked-updates-since-april