Epistle of Barnabas (early Chrisitan text) identifies Jesus as the Son of Man from Daniel 7.
Epistle of Barnabas 12:10 in Gregory R. Lanier, Corpus Christologicum: Texts and Translations for the Study of Jewish Messianism and Early Christology (Peabody, MA: Hendrickson Academic, 2021), 627 (Logos ed.)
ἴδε πάλιν Ἰησοῦς, οὐχὶ υἱὸς ἀνθρώπου, ἀλλὰ υἱὸς τοῦ θεοῦ, τύπῳ δὲ ἐν σαρκὶ φανερωθείς. ἐπεὶ οὖν μέλλουσιν λέγειν, ὅτι Χριστὸς υἱὸς Δαυείδ ἐστιν, αὐτὸς προφητεύει Δαυείδ, φοβούμενος καὶ συνίων τὴν πλάνην τῶν ἁμαρτωλῶν· Εἶπεν κύριος τῷ κυρίῳ μου· Κάθου ἐκ δεξιῶν μου, ἕως ἂν θῶ τοὺς ἐχθρούς σου ὑποπόδιον τῶν ποδῶν σου.
Again see that Jesus—not as son of man but Son of God—was revealed both as a type and in the flesh. Since, therefore, they were about to say that “the Anointed One is son of David,” David himself prophesied, fearing and knowing the error of sinners, “The Lord said to my Lord, ‘Sit at my right hand, until I place your enemies as a footstool for your feet.’ ”