If you use Samsung music app hit the three dots top right corner/settings/control music from lock screen. Whilst listening to music this give u a full screen widget that supersedes the lockscreen. See photos bellow 👍🏾
Also, I jus tried Spotify on the Samsung music app, and it just redirects to Spotify. Doesn't actually play in the app. So the only way we can get full screen controls, is by our own, on device media. And no one does that anymore really. So, 3rd party - or even Google integration would be greatly appreciated!