The game has recently switch backed to DirectX11 by default, after discovering performance issues that were caused by DX12. If the reversal switch to DX11 negatively impacts you, you can switch to Dx12 through the graphics options and restarting your game.
Warning: The game intends to support DX12 SM6, which currently has issues on AMD GPUs on UE5. As a result, the toggle is currently unavailable on AMD GPUs and generally older GPUs.