The best alternatives to Songstream Player are YTMP, VOX for iOS, and reEmbed. If these 3 options don't work for you, we've listed a few more alternatives below.
YTMP : YouTube Music Player is the First and the Only YouTube Music Player that lets you play any youtube video as audio with tons of features such as Background play, Playlist merger, No Ads, and many more for free while saving up to 98% of your data.
This extension allows you to watch your favorite online videos on your Roku & Chromecast. You just need to create an account on https://kastfy.com where you will be presented with very simple instructions to cast the videos.