How can I prevent my material from being used to train AI?

You can specify in the metadata of your material that it may not be used for training AI.

To do this, start at your workspace and open the menu options (three dots) for the material you want to add AI info to. Pick edit info from the dropdown menu to get to the metadata dialog.

In the following window, click on the manage license tab and open the information about AI origin and usage drop-down menu.

Uncheck the box in the Usable for AI training section and then save your changes.