I am extremely confused and frustrated with the UI change to put new messages at the top of Teams. Why are new messages at the bottom in Chat, and at the top in Channels? Please consider making them consistent.
Second, having new messages at the bottom has been a familiar UX pattern across many popular applications for decades. The pattern appears in Slack, Discord, iOS Messages, heck even AOL Instant Messenger. For you to put it at the top makes it appear as though you simply tried to copy Facebook's Feed, which is not a good analog for Teams.
It's also frustrating that I cannot turn the sort option off. The change was forced on my application and there is no way to change it back. This makes me less excited to try any other "experimental" features you have coming down the pipeline. Please listen to your users.