I just finished going through the "De-Mystifying Mindfulness" course on Coursera and they do warn about the fact that "mindfulness" has become an industry and that the people who offer courses are often unqualified to teach them.

MBSR and MBCT course with qualified teachers do have a very good track record and solid scientific backing.

There are also some replicated studies of the synergy between mindfulness and psychedelics. https://www.sciencedirect.com/science/article/abs/pii/S10538...