I see that there are slight variations but nothing major.
(NA28) 13 προσδεχόμενοι τὴν μακαρίαν ἐλπίδα καὶ ἐπιφάνειαν τῆς δόξης τοῦ μεγάλου θεοῦ καὶ σωτῆρος ἡμῶν ** ⸂Ἰησοῦ Χριστοῦ⸃**, I (NA28) • 13 ⸂ Χριστου Iησου א* F G b ¦ Iησου 1739 ¦ txt א2 A C D K L P Ψ 0278. 33 . 81 . 104 . 365 . 630 . 1241 . 1505 . 1881
To your point: a definite article placed immediately before the term Savior
I found entries in the BDF grammar which also cites Winer-Schmiedel Grammatik in my research that are omitted from Wallace's treatment on the subject even though he quoted part of the same reference, the part he felt supported him, the AT Robertson citation.
Here is BDB followed by comments as cited in my paper.
15 (3) Cf. 2 P 1: 1 (but here S has κυρίου for θεοῦ, probably correctly; cf. 11, 2: 20, 3: 2, 18); however σωτῆρος ἡμ. ̓Ι.Χρ. may be taken by itself and separated from the preceding (cf. §268(2) for the omission of the art. elsewhere). Cf. W.-S. § 18, 7d(!); Mlt. 84 [134f.]; A. T. Robertson, The Greek Article and the Deity of Christ (Exp. VIII 21  182–8). (BDF, 1961) -- Note the reference also to W.-S. §18 where Winer-Schmiedel Grammatik refers to the lack of the article at 2 Peter 1:1 and Titus 2:13 allows for two persons to be in view. See (Blunt, 2019) for the complete quotation in German.
The significance of this is that according to the BDF grammar that Wallace frequently cites, in Titus 2:13 and 2 Peter 1:1 it is not necessary for the article to be present for the second term to be considered definite.
Here is Winer-Schmiedel Grammatik in German.