Grayjay is a video player for YouTube and other services. I believe its ad-free and "algorithm-free", meaning it just gives you every video from every channel you subscribe to, in chronological order. It was initially for Android and iOS.

It's backed by Louis Rossmann, who does a lot of right to repair advocacy, among other things.

"Grayjay combines video content from multiple platforms, such as YouTube, PeerTube, Twitch, and others, into one app, removing the need to switch between different platforms."

Aside from vaguely implying it’s some kind of media player that plays content from the internet, that doesn’t tell a whole lot.

Some screenshots would be a nice addition to their page.

There are a bunch of screenshots on the linked page, you might have a plugin that is interfering with the content if you don't see them.

Screenshots disappear for some reason on mobile. Home page has screenshots but only of the mobile app.