I'm always surprised that Kratom (https://en.wikipedia.org/wiki/Mitragyna_speciosa) doesn't come up more in these conversations. In addition to being a powerful painkiller, it helps manage opioid withdrawals.

I believe it's still somewhat legal for consumption in the U.S., though other countries have been moving to ban it to varying degrees, since it can be used recreationally, though it isn't known to produce the same intensity of euphoria as opioids, and can also be addictive, though I don't believe it to produce as severe withdrawals as opioids.

All in all I think it's a sadly understudied and underutilized medicine, which is the unsurprising result of pharmaceutical companies having less incentive to study plant medicines