別に言い伝えがあるっていうだけだよ
How does it differ from just 別に言い伝えがあるだけだよ?
The って in っていう is a contraction of the と in という which is used to quote something and is usually translated as "That is to say" or "That is" or something like that (depends on the context) and sometimes it gets lost in translation (unless you are translating literally).
Here the quotation is applied to 「別に言い伝えがある」so「別に言い伝えがあるっていうだけだよ」would translate into "That's just another (not especially interesting\important\unique\special) legend\tradition, you know".
Without っていう it would translate as "There is just another legend, you know" which is kind of weird.
Here are two videos explaining more about the と particle for quotation: