To prevent all speakers from displaying in the homepage and display only the keynote speakers, do the following:
1. First disable the default "Speakers" widget to hide all speakers from displaying on the homepage.
2. Go to Roles & Access Control and create a new role "Keynote speaker" (which would also create a widget under homepage widgets).
3. Go to Contacts, click on Speakers tab, and assign the "Keynote speaker" role to all speakers who are Keynote speakers using the Bulk Edit tool.
4. Then, go to Website & Apps > Homepage widgets and enable the widget titled "Keynote speakers". That's it.
