To save others the disappointment I just felt: this is only available in the US.
replyGenuinely curious, is this sarcasm? I don't use any YouTube mobile app, but doesn't "new and unseen [...] videos predominantly from people I follow but occasionally interspersed with others' you think I might like in a similar vein" just sound analogous to "recommend me videos I'd like to see".
replyIt is also available in the PWA. Yes, it's a real feature with a Gemini-powered prompt. Yes, GP describes a prompt that approximates the actual algorithm.
replyI just wrote "nothing but Sesame Street parodies" and the feed does what it says on the tin.