PocketTube - Group YouTube subscriptions into YouTube folder. Video Deck for Youtube. Mark as watched videos. Filter YouTube video. Youtube mode
Video Deck for YouTube - Control videos that are uploaded by your favourite YouTube channels.
NewPipe - NewPipe is a lightweight YouTube front-end for Android.
Invidious.io - Invidious is an alternative front-end to YouTube.
VC Starter Kit - Everything you need to look like a Venture Capitalist
Better Subscriptions for YouTube™ - This extension for Firefox and Chrome aims to make navigating YouTube's subscription grid easier by allowing users to hide watched videos