Your Mass card is "good" in RI in the fact that RI recognizes your license and you can have meds.
HOWEVER, a caregiver can't exchange meds for a donation. They would have to literally give it to you for free. Also, since you're not in the RI system, you can't use RI dispensaries (you need a dispensary to be signed on as a caregiver to shop there).
So, there really is no legal way for you to get meds in the state but if you have them, the state recognizes your card.