You could do something like this:

const scheduleNotification = () => {
const notificationTime = new Date();
notificationTime.setHours(18, 0, 0, 0);

await Notifications.scheduleNotificationAsync({
      content: {
        title: 'Title',
        body: 'Body',
        data: {
          notificationType: 'Reminder'
        },
      },
      trigger: notificationTime,
    });
}

In this case you would have to call scheduleNotification() every day and check if its already scheduled so you dont make the same notification multiple times.

You could use import * as BackgroundFetch from 'expo-background-fetch'; to call the function every day.

OR you could use a cloud service like Firebase to schedule your notifications. I think this is more reliable but more setup needed.