Five apps
One you buy, and the clients that show it.
Decky runs on your Mac or Windows PC. The clients that show a screen are free, because the person watching today is the one who presents next week.
Which one do I need?
Get Decky for your Mac or Windows PC. Get Decky Display for an Android device, a Mac or a Windows PC. Decky Air is for when you want a screen and nothing installed on your Mac at all.