I have given the Qlik Sense R integration a go and it works. But would warn that it is not for the faint hearted if you do not know R as first you will have to learn R.
I had a go at it purely for the intellectual challenge and claim no expertise, apart from I managed to get it work.
Unfortunately I could find no practical use case for it my work environment, although I expect different work environments could well have practical use cases.
Yup, loads of good stuff in that group Advanced Analytics Integration well work checking it out.
It used to be a closed group and the moderator moved onto other things. I still have access to it but if you cannot get access then maybe ping sli a message she may be able to sort.
Also check out Qlik Branch there is some useful stuff re R there as well.