You can set a routine to set the media volume to 0 at a certain time or "while sleeping" or even create a shortcut on the home screen. Another, non-free option would be a cheap Bluetooth speaker / headphones (you can pick up either for about a tenner on the low end), the phone remembers the volume set for the output so if media volume is 0 before using a Bluetooth device it'll revert back to 0 once the device has been disconnected. Another, far FAR more complicated option would be home assistant, you could have it detect when music/audio is not playing then set the volume to 0 when it stops (you can also add far more conditions like when you're at home or when the phones on charge or even only when it's raining if you want, there's thousands of possible conditions!!). Also, now I think about it, I'm sure there's a way to set different volume levels for different apps, I can't remember how off hand though I'm afraid
