According to a developer post at Steam, the developer needs some extra work and optimizations to do for DirectX 12 and needs more time to ensure it will deliver a "compelling" experience. The game will only work in DirectX 11 mode which means it will lack support for Asynchronous Compute, which is a bit of bad news for AMD and Radeon owners.
It is not all bad news as the developer promises that DirectX 12 support is coming and should be ready in early September, or to be precise, in the week of September 5th.
Earlier this week, Eidos released both minimum and recommended system requirements for Deus Ex: Mankind divided which were rather high, with GTX 970 or AMD Radeon RX 480 as the graphics card that you will need in order to play the game at 1080p.
The minimum requirements included an Intel Core i3-2100 or similar AMD CPU, at least 8GB of RAM and Radeon HD 7870 2GB or GTX 660 2GB graphics card, while the recommended listed Core i7-3770K CPU or AMD FX-8350 CPU, 16GB of RAM and aforementioned Nvidia GTX 970 or AMD RX 480 graphics card. The minimum requirements also included Windows 7 SP1 64-bit OS and 45GB of HDD or SSD space while recommended one are sticking to Windows 10 64-bit OS and 55GB of HDD/SSD space.
Deus Ex: Mankind Divided will start pre-loading on August 19th and officially be ready for play on August 23rd.