Unpopular opinion, but phones these days don't really need more buttons, but less. We have a huge touch screen after all, let's take better advantage of it!
"Action button" - Android phones have had a long press of power button be the assistant button since Android 12, just set your "assistant" as whatever action you want (e.g. with Tasker).
Sleep/wake button - can be the power button for now, but also don't forget double-tap on the home screen/lock screen/status bar.
Power off/on - virtual button since Android 12, physical button for turning on. In case of emergency, I guess hold down for longer or do something like triple-tap.
Volume keys - every video app should use onscreen gestures, same could be applied for music. In other contexts, statusbar or side swiping gesture could suffice, plus a notification shade slider like some OEMs already provide.
Unpopular opinion, but phones these days don't really need more buttons, but less. We have a huge touch screen after all, let's take better advantage of it!