Divinity: Original Sin 2 Definitive Edition will support native 4K resolution with HDR on Xbox one X and dynamic 4K with HDR on PS4 Pro.
Sadly, there are no plans to add HDR to the PC version for now.
Source: N4G PC Divinity: Original Sin 2 Will Support Native 4K & HDR on Xbox One X, Dynamic 4K and HDR on PS4 Pro