Theme picker is a dropdown now, grouped into accent colors and full palettes, and palettes bring their own type and shadows with them. Bubblegum is gone; Neon and Breeze replace it.
Sign-in is Google-only. The cookie-paste box and its DevTools walkthrough are gone, since the login window does the same job without the ceremony.
On Repeat no longer inherits the queue slot a song was played from: no stray Listen Together attribution on the rows, and playing one drops you into the right context instead of Next in queue.