To see all available public channels you can join that you’re not already a member of, select the + icon at the top of the channel sidebar, then select Browse Channels. Search for channels by name or scroll through the list. Select Join next to any channel to become a member of that channel.
Want to see all of the channels you’re already a member of? Select Find Channel in the channel sidebar to see all of the channels you’re currently a member of across all of your teams, including public and private channels, direct and group messages, channels with unread messages, and threads. Channels you have muted aren’t included in results.