Sigh ... the tutorial, "Ruby's Adventure: 2D Beginner" is a 3D project.

I restarted the tutorial and changed it to 2D using the menu "Edit -> Project Settings... -> Editor -> Default Behavior Mode".

I'm leaving this here in case anyone else hits this relatively minor snag.

The tutorial, "Ruby's Adventure: 2D Beginner" is a 3D project.

I restarted the tutorial and changed it to 2D using the menu "Edit -> Project Settings... -> Editor -> Default Behavior Mode".

Next, I followed Cedric Degottex's suggestion in the comments for the tutorial by opening "Window > Package Manager", and installing the "2D Sprite" and "2D Tilemap Editor" packages.

I'm leaving this here in case anyone else hits this relatively minor snag.