You know the guy who starts a repo with great passion, writes a ton of crap and shares it without any README
so nobody actually can use it? Welcome to his GitHub!
You can instrument your entire Kubernetes cluster by only using OpenTelemetry collectors and send the telemetry data you have collected to any backend you want.
You can instrument your applications with OpenTelemetry SDK and send all your telemetry data from your applications to your desired backend.
Check out how to generate Prometheus metrics as well as how to scrape and query them per PromQL with Grafana.
You can use this repo to figure out how much data your Prometheus instances are scraping.