Suboxone at 2mg will block kratom almost completely, kratom's alkaloids have some effects besides opioid agonism so it does do a tiny bit but barely, and not the opioid aspect of it at all.
By the way, 2mg of suboxone is not actually a low dose, in fact 2mg is enough to completely saturate the receptors, and is about as effective as higher doses, except lasts a lot longer. At 2mg, I have found that after about 24 hours or maybe slightly more without bupe, I can start to feel kratom a little bit, but it takes about 48 hours to get a relatively normal effect.