Just like Invidious, Piped offers a free and privacy-friendly to YouTube.
The advantage of Piped is that it works with SponsorBlock, so you don't waste time putting up with sponsored parts of videos. I've only mentioned the features I find most useful; a more detailed list is available on the project page.
Some disadvantages compared to Invidious are that it does not allow you to sort the videos of a channel according to age or popularity, but simply shows the latest videos of the channel; there is no button to download videos and audio; you do not see a thumbnail of the frame when hovering the mouse over the timeline; the thumbnail of the video does not appear when sharing a link...
