Telegram X is an official client from the Telegram development team. It excels in speed, ease of use, and perfect animations.
It has a beta release channel on Google Play and you can easily OPT-IN for testing via the links down below.
New beta reports and tips for beta testers can be found in our recent reports section with the latest posts about Telegram X beta testing. In addition to that, TestingCatalog tracks the history of recent Telegram X beta updates and changelogs.
If you are looking for the de facto Telegram app for Android, you can also check out this guide on "How to become a beta tester for Telegram on Android".
App Description from Google Play
An alternative Telegram client based on TDLib, with higher speed, slicker animations and experimental features.
Here you can find a list of helpful posts about Telegram X beta testing by TestingCatalog.