Hi Felix, welcome to the SonarSource Community!
Administrative note: I moved your post to be its own fresh topic since you replied to a year-old conversation with a slightly different angle (the involvement of jest).
Comparing your lcov.info contents with the one generated in my example Angular project, the clear difference to me is relative versus absolute paths. I don’t know jest; is there an option to have it generate absolute paths instead? Give that a shot.