The User Role widget is a ComboBox when drug into the Data View. In the solution migrated to 10.6.2, it is a Input Reference Set Selector. The instructions and object need updating for the control so that Select Page can be found. 10.6.2 is not in the selection list, but is what I am using:
I downloaded the Chapter 6 solution and migrated it to 10.6.2.
Then, I was able to see the proper widget and added an Input Reference Set Selector, set the properties accordingly and removed the combobox.
The Crash Course is based on Mendix 10.0.0, so the default behavior eg for creating pages and maybe even some core settings is different compared to 10.6.2. Best to follow the Learning Paths in the exact version that is mentioned.