Yes and no. It all depends.
Natives don't add anything. They just use water and that works just fine. An acid is not needed at all. When you brew a cup of coffee or tea do you add an acid? Of course not, and you still extract the caffeine. Only certain alkaloids need to be pared with certain acids in order for their water solubility to increase.
Some alkaloids are more soluble in certain acids than in pure water, even when in salt form. But this is not true of all alkaloid salts.
For example, harmine hydrochloride is very poorly soluble in dilute hydrochloric acid. Its more soluble in pure water. But then harmine acetate is the opposite, it’s far more soluble in dilute acetic acid (vinegar) than in pure water.
The results depend on the alkaloid, the plant, and the acid of choice. So there is no one answer to your question.
To answer the question, the question needs to be more specific. We need to know the exact plant, the exact acid, and all the alkaloids in question. Without that information, there is no way to answer the question accurately.