I am not familiar with using unicode however in python I can open a file with the path you supplied with both cv::VideoCapture and cudacodec::VideoReader in OpenCV 4.8.0. e.g.
cap = cv2.VideoCapture(‘d:/media/CU测试汉字_K988+11/K0+000.265’)
and
reader = cv2.cudacodec.createVideoReader(‘d:/media/CU测试汉字_K988+11/K0+000.265’)
As cudacodec::VideoReader uses cv::VideoCapture to open video files I am suprised that for you one worked and the other did not.
Maybe there is an error somewhere else, can you supply the exact code you are using and I will try it on my setup?