Do not use random APK sites. Go to the official developer's GitHub page: github.com/yuliskov/SmartTubeNext
If you are searching for a fix for the legacy "Smart YouTube TV" app (version 6.x), the answer is no—it is dead and broken. You must upgrade to . smart youtube tv 617 740 work
By following the sideloading steps in this guide (downloading from GitHub, installing via Downloader, and tweaking the video settings), you will eliminate Error 617 (playback failure) and Error 740 (login failure) completely. Do not use random APK sites