To play downloaded 4K H.265 movies on a Samsung smart TV, you'll need to convert the files to a format that's compatible with your TV. One way to do this is by using a video converter software, such as EaseFab, which can convert H.265 files to H.264, which is a format that's supported by Samsung smart TVs. Simply load your H.265 video files into the software, select the Samsung TV preset, and click convert. Once the conversion is complete, you can transfer the converted files to a USB drive and play them on your TV.
Alternatively, you can also use a media streaming app such as Plex to transcode HEVC files to H.264 format, which is compatible with Samsung smart TVs. Simply download and install Plex on your TV, and then add your H.265 files to the app. Plex will automatically transcode the files to H.264 format, allowing you to play them on your TV without any issues. This method is convenient because it doesn't require you to convert the files beforehand, and you can simply play them from the app.