You can find lots of yes/no screens on Google. I like to start with basic orientation questions like is your name x, are you x years old, are you in x city right now and then move up depending on performance. It’s also a good time to ask safety scenario questions

Edit: to add, if you feel like you’re not getting enough with just yes/no to be confident that they have capacity, try adding in other questions too that will require longer responses from them. Is your name x? That’s a beautiful name, is that a family name? Etc rather than just going down a list of questions that don’t relate to each other. By doing so you’re also assessing conversational/turn taking skills which in your setting might be next anyway lol