Different customs of saying the 27th psalm

My custom is to say the 27th psalm (“By David, Hashem is my light and my salvation”) after maariv, and not after minchah, which is the custom of congregations that pray nusach Ashkenaz (Lithuanian tradition). But I pray minchah in a synagogue that follows nusach Sephard (Chassidic tradition), and they say the 27th psalm after minchah, and not after maariv. I wanted to ask the Rabbi, should I say this psalm after minchah, or after maariv?

You should say it together with the congregation after minchah. As for maariv, if you pray in a place, where they don’t say it, you don’t have to say it again, since you already said it during minchah. However, if you are going to pray maariv in a place that follows the Ashkenaz custom, where they say this psalm after maariv, you should say it with them again, so as not to separate yourself from the community.

Have a good and happy year!

See Mishnah Berurah, ch. 581, subsection 2