On August 7, some beta users got a new message from a verified Telegram channel with an invite to join a new public testing channel for Telegram beta.
Previously, this process was organised via a Telegram Memes channel and was a bit chaotic. Now, beta testers who joined this channel may enable notifications in order not to miss new tests that are scheduled by the Telegram team.
The purpose of such tests is to stress test certain features that are meant to be used by a big number of users at the same time. Currently, Telegram is testing its new quiz mode that can be integrated into group or channel video/audio calls in the future. Telegram has a quiz directory on the website that you can try beforehand as well.
This new channel is private and you will have to wait for an invitation from Telegram. Alternatively, you can try to use this invite link as well. Did you get it already?