The most popular tool for this purpose is the plugin. It exploits how Discord handles data: the Discord API often sends information about all channels in a server to your client, even those you don't have permission to view. The standard Discord app simply hides them from your sidebar, but a plugin can force them to appear.
If you think you should have access to a specific project or discussion, send a polite DM to a server administrator. Final Verdict read locked channels discord plugin download