The fact that it is natural means nothing. Kratom can cause addiction. It is active at opioid receptors
Morphine occurs in nature!
Diaceytlmorphine (heroin) is simply a prodrug of morphine. Diacetlymorphine is so close to morphine that it is often referred to as a "semi-synthetic" opioid.
Another problem with kratom is you don't know how much of the active ingredients you are getting.
The active ingredients are mitragynine and 7-hydroxymitragynine, which are (partial) agonists at the mu- opioid receptor. At least with a prescription drug, one can measure their dose.
There is no reason to assume that "natural" implies "safer."
Kratom stops opioid withdrawal because it is substituting as an opioid.