Dead? How can I tell?

Try using this image: [Beta] Patchbox OS image 2020-11-23

Take it one step at a time - first ensure that you’re getting visual display and you can control the system using your mouse & keyboard, alternatively you may use ethernet cable and ssh or remote desktop like VNC to access the device. Once that is sorted out, then move on to putting on the Pisound and installing the software you want to use, etc…