Rinse the sauerkraut only if it is fierce, and keep some of the brine either way — it is the acid that stops this being heavy. Lentils and acid do not cook together, so the kraut goes in once the lentils are already soft.
It did not make it into the plan for these seven days.
The method above is what decides the dish, not a step-by-step recipe. The link runs a web search on the name: this page has no vetted sources of its own, and will not invent any.