Could it be another model?? Yes, e.g.ISO33061 covers the same scope. The content is the same, just arranged slightly different.
In Whitebox we find CMMI to be the best and most operational model. And this version is free to download here.
You ca find a lot of inspiration in it. But remember that it is not telling you exactly what to do. It is telling you what the best are typically doing, but you always need to apply your professional judgement to decide what is important to you. Reading the model end-to-end is tough! But seeking inspiration is recommended.