there are only few differences. Many of the differences are merely linguistic.
The Ramban rarely mentions it. So, if other Rishonim refer to it one time less than the Ramban, they won’t mention it at all.
There are many differences, not just linguistic. Also, many linguistic differences are significant, since it is a ‘Targum’.
The Ramban does mention it, in your words. And other Rishonim do refer to it. Like the Rikanati, who lived in the Ramban’s times, refers to Targum Yonasan on the Torah. Often. Tosafos mentions Targum Yonasan on the Torah (a”z 59a). Not only do they mention it, they also brings there a machlokes between the Targum Yerushalmi and the Targum Yonasan on the Torah on what Har Seir is.