Cannot find name "T" Typescript

The generic that React.FC accepts is used to type the props object. So instead of inline typing your props, you would create an interface that accepts its own generic:

interface ListProps<T = unknown> {
  items: T[];
  render: (item: T) => React.ReactNode;
}

and then declare the interface that you will pass into the ListProps generic:

interface YourGenericType {
  el: string;
}

To consume these two interfaces together with your component:

const List: React.FC<ListProps<YourGenericType>> = ({ items, render }) => {
  return (
    <View>
      {items.map((el, i) => (
        <Text key={i}>{el}</Text>
      ))}
    </View>
  );
};

Edit: I would also add that unless you need access to an implicit children type, it's recommended that you don't use React.FC as a function type signature. See here for more info. With this in mind, I would type your List component like so:

const List = ({ items, render }: ListProps<YourGenericType>) => {
  return (
    <View>
      {items.map((el, i) => (
        <Text key={i}>{el}</Text>
      ))}
    </View>
  );
};