iOS does not provide a direct way to add reminders to Due using Siri.
In order to use Siri to add reminders to Due, you'd need to setup Auto Import in Due.
With Auto Import set up, you'd first use Siri to add reminders to Apple's Reminders app, which Due will then import when possible.
Setting Up Auto Import
- Decide on the iOS device that you'd like to enable Auto Import on. This device should be the one that you use Due with most often, which is most likely your iPhone. It is important to only setup Auto Import on one iOS device to prevent duplicates and other conflicts.
- On the chosen iOS device, open Due app > Settings > Auto Import. If this is the first time you're accessing this function, Due will request for permission to access your reminders.
- Choose one or more lists that you'd like Due to automatically import reminders from. It is recommended to choose the list configured in iOS Settings > Reminders > Default List. Note that (a) only reminders with due dates will be imported, and (b) the original reminder will be deleted from Reminders app once it has been successfully imported into Due.
Once you've set up Auto Import, you can begin the use Siri to add reminders to the lists configured in Step 2.
If you've selected the default reminders list, you can simply add a reminder by saying something like “Remind me to pay bills tomorrow at 10 AM”. If you've selected other lists, follow the tips here on how to use Siri to add reminders to specific lists. The reminder will be saved into Apple's Reminders app, which will then be imported by Due each time you launch Due, or periodically in the background via Background App Refresh.*
Important Notes About Auto Import
- Only reminders with due dates will be imported by Due. Remember to specify a due date when adding reminders with Siri if you'd like the item to be auto imported.
- The original reminder will be removed from Apple's Reminders app once it has been successfully imported.
- It is possible that Due may not have the chance to import a reminder before it becomes due. This is more likely if the due date of the reminder is very soon (before you manage to launch Due, interact with any of Due notifications, or before the next Background App Refresh). In this scenario, the reminders that have yet to be imported will be fired by Reminders app instead of Due.
* Background App Refresh is an iOS technology that periodically wakes an app in the background to check for new content. Exactly how often an app is woken up in the background is mostly dependent on a variety of factors beyond the app's control, including your usage of the app, your device battery life, network connectivity, etc.