Looks like Reddit user Spacefish008 got Portal with RTX running on a 5700 XT. They note that they get “~45 FPS on 846x643” on High settings. All that’s needed is the RADV_PERFTEST=rt,emulate_rt %command% launch parameter. The OP explains how this works: It uses DirectX and DXVK exposes the DXR APIs to the game if it detects raytracing support in the underlying Vulkan driver. The Vulkan driver is RADV, which can emulate raytracing via shaders on older-gen AMD GPUs like NAVI10 / RDNA1.