Learn tab in Photoshop

The panel went away, but the feature did not go away. It got moved.

What Adobe did was upgrade the Edit > Search command to be more holistic and training-oriented; it’s now the Discover window. That now provides suggestions before you type in anything, with Hands-On Tutorials being the top item. If you do type something, Discover will list more focused results. It also floats on top so it is not hidden by other things while you are referring to it.

How you can teach this is to get students into the habit of pressing the shortcut for Edit > Search (Command-F/Ctrl-F) that students might already be habitually using in other applications. Through that shortcut, a student can find Photoshop tools, commands, shortcuts, tutorials, quick actions, help articles, and other links all related to whatever they typed in. Or, if they don't like keyboard shortcuts, get them into the habit of clicking the search icon (magnifying glass) near the top right corner whenever they need to learn or can’t remember something.

For example, I often forget where the Paint Bucket is hiding in the Tools panel, but Command-F not only finds it but highlights it for me in the Tools panel. The Discover window is not perfect, but what it is now is a one-stop source to all of that.

More info:

Feature summary | Photoshop desktop (October 2020 release): Learn more directly in the app

If the tutorials you were using are no longer there, they must have changed them. If you want to continue the unit you were teaching it would be good to drop back to the previous version of Photoshop, which you can still install from the Creative Cloud desktop app.