This is not a regression. Tested in //UE5/Release-5.2 CL26001984.
Hardware Accelerated Video Decoding requires DirectX 11, but it appears the combination causes media players to only render a black video on play back.
The video plays without issue.
The video is black in the Media Player.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-194800 in the post.