Microsoft published a 1.0 (production) API version for MS To Do in November 2020, but it still lacks several essential features (Push sync, manual position, steps, categories, etc.).
aCalendar will add MS Todo support with version 2.5.
We will improve compatibility timely apon API improvements by Microsoft.
Please do not rate aCalendar down for shortcomings of Microsoft (and generally, please do not rate indie apps down for shortcomings of major corporations)