Microsoft plans to roll out the new Teams channels experience to commercial and GCC tenants in mid-June 2023 with GCC-High and DoD tenants getting the software in July. The new UI gives Teams channel conversations a visual makeover and adds some useful features like being able to pop out conversations and using Viva Topics in messages, Moving the compose box to the top of the screen takes a bit of getting used to, as does the way that Teams creates a focus on reading a conversation. Overall, the new UI is an incremental rather than a radical improvement, which is probably what people want.
https://office365itpros.com/2023/05/10/new-teams-channels-experience/
