Today December 2nd I received this message from Telegram service notifications about my outdated Desktop app version:
Please update your app to the latest version. The version you are using is out of date and will stop working soon.
...In Ubuntu 20.04.3 LTS the latest released version of Telegram Desktop app is 2.1.7, I ask to you for upgrade soon the repo for LTS with the last version of Telegram, please!
Here is a related question for ARM.