The latest .exe I downloaded appears to do it, to use GPU for rendering I think is automatic once you use NVEnc version of h.264 or h.265, here's the command line I used with newest ffmpeg downloaded from ffmpeg.org for my testing:
.\ffmpeg.exe -f concat -safe 0 -i frames.txt -c:v h264_nvenc -b:v 3000k -r 29.97 "O:\VideoProd\upscale\output.mp4"
notice the codec h264_nvenc, with this in task manager I see ffmpeg using 60 - 90% GPU and render completes in about 45 minutes for a series of frames that took about 5 hours in QualityScaler. My upscale project videos don't have audio so fortunately I didn't need to figure that out but I imagine however you are already doing audio should continue to work.