I'm still on the fence about the "everything" representation in the Home sidebar, and I'm glad that my manual Chat channel order is represented there, but forcing the dedicated Chat window to sort in order of recent use seems bizarre to me. I depend on my manual sort order to quickly get where I need to go in Chat, I use that "most recent" sort order.

Even if you only offered Alphabetical as an alternative, it would be an improvement — at least then I could reliably find any channel where I expect it to be. But Manual/Custom order is my personal preference, I just want a consistent structure that groups things in the way that makes sense for me and my org.