is there a chance that PROres and HAP with alpha could be played in ue4 with directx12 enabled ?
hap alpha is dx12 friendly since its gpu decoded, prores 4444 is more cpu bound and d3d12 support depends on the media framework build. if your source has alpha, try hap alpha first on dx12 it tends to just work. safest for alpha in general is still exr/png image sequence with alpha via ImgMediaSource — zero codec headache. alpha video player from fab Alpha Video Player - Transparent Video UMG Widget & UI Media Component (UE5) | Fab handles all three (prores 4444, hap alpha, webm vp9 alpha + sequences) so you can keep the same widget and just swap the source file, Win64