ActiveInbox doesn't have its own app, but because of the way it works with Gmail, you can actually make use of your organized email anywhere.
Understanding how ActiveInbox organizes email
ActiveInbox uses regular Gmail Labels to organize your email - yes, that includes Due Dates!
(The only things that aren't managed this way are Sub Tasks and Notes. They're not available on mobile at this time.)
For due dates, there is a label to represent every day. It's in the format ZD/yyyymmdd. So, 25th December 2030 would be ZD/20301225.
Similarly, your projects match labels that begin with P/. So, if you have a "Launch 3.0" project, its label would be P/Launch 3.0.
If you wish, you can create your own custom workflows.
Making use of this on mobile
You can give any email to a due date, just by giving it the appropriate Gmail Label in any email client you like. E.g. for 31st October 2022, you'd give it the label ZD/20221031.
And to review all emails for today, just browse your label list in the app of your choice, and find the corresponding date label.