AFAIK the scientific consensus is no amount of radiation exposure is beneficial. There have been some theories going around about how a small amount of radiation can be beneficial but I think that's been proven not to be true.
For the search-adverse readers, here is an introductory discussion on the topic, from a US vs Europe point of view.
On the other hand, LNT utterly fails to address the well-documented trend that people in areas of high background exposure experience lower rates of cancer. The mechanisms of this effect are not understood, though often hypothesized, nor is there any strong argument for a particular upper limit (though plenty of known examples, like smoking and frequent flying, lie beyond it.)
I wouldn't advise anyone microdose on radon, nor ignore the risk of radon if you're in the habit of keeping your modern home closed up... but this matter is not settled as you portray.
Edit: sorry for my other flippant comment. The confident misunderstanding of science got me a little worked up.