This will not work for devices other than Raspberry Pi 3B (specifically devices that aren't using ARMv8 processors), or if you are using a custom soundcard that shows up as anything other than type hw card 0.

The easiest way to install Prometheus is by downloading the prebuilt executable provided here under Releases, unzipping them, and then putting them in rc.local

sudo apt install unzip
wget /~https://github.com/gilgameshskytrooper/prometheus/releases/download/v2.2.3/prometheus.v2.2.3.zip
unzip prometheus.v2.2.3.zip
rm prometheus.v2.2.3.zip

In /etc/rc.local, add the following line at the end:

/[path_to_prometheus]/prometheus &

When you restart the Pi, prometheus will automatically run. The & at the end is to ensure that bash runs prometheus, then sends it to a background in order to finish other boot processes.