Very likely, Dan Fefferman's hypothesis (espec. in the last paragraph) is correct. Emanuel Tov could be very useful (Textual Criticism of the Hebrew Bible, 3rd edition, 2012, pages 53 [and ft. # 67]) in this instance (all the bold emphasis from now on is mine).
Indeed, he states (I've decoded the symbols Tov scatters throughout his essay, putting their equivalents in square brackets): "In Judg. 18:30 [...], a suspended nun corrected an original [...] 'Moses' to [Manasseh] [...]. This addition was apparently meant to correct an earlier reading that ascribed the erecting of the idol in Dan to one of the descendants of Moses (b. B[ava] Bat[hra]. 109b). The addition therefore indicated a deliberate content change [...]. Many manuscripts and editions of [MT] (as well as [the Jerome's Vulgate]) read the corrected form 'Moses'. The two forms are also reflected in different manuscripts of [the Septuagint][...] 'Moses', in the [Alexandrine manuscript] [...]."
The John MacArthur's Study Bible comments: "Some manuscripts say 'son of Manasseh', others 'son of Moses', which may be more probable as Gershom was a son of Moses (Ex. 2:22; 18:3)." [ad locum]
The New Oxford Annotated Bible (5th edition): "The origins of the shrine at Dan (1 Kings 12.25–30). 30: Jonathan son of Gershom, son of Moses, Jonathan belonged to the third generation after the Exodus, yet by now scores of years had passed according to thechronology of Judges (see 3.11,30; 5.31; 8.28); this suggests that this episode is placed here for thematic rather than chronological reasons. Pious scribes seeking to protect the name of Moses from association with an illicit shrine connected to his grandson inserted the Heb letter 'nun' ('n') above his name in the Hebrew text, turning 'Mosheh' (Moses) into 'Menashsheh' [...]." [ad locum]
Robert Alter's 'Prophets': "Jonathan son of Gershom son of Moses. At the very end, we are given the name and genealogy of the Levite. The Masoretic Text [better, some manuscripts’] inserts a superscript nun in 'Moshe', 'Moses',turning it into Menashe, Manasseh, but this can’t be right because Gershom was the son of Moses and Manasseh is not a priestly tribe. Rashi aptly explains the orthographic oddity: ‘Out of respect for Moses, a nun is inscribed in order to change the name.’
Adam Clarke's Commentary on the Bible: "Instead of מנשה Manasseh, the word should be read משה Mosheh, Moses, as it is found in some MSS, in the Vulgate, and in the concessions of the most intelligent Jews. The Jews, as R. D. Kimchi acknowledges, have suspended the letter: נ nun, over the word [...] [so] by the addition of the points, they have changed into Manasseh, because they think it would be a great reproach to their legislator to have had a grandson who was an idolater. That Gershom the son of Moses is here intended, is very probable. See the arguments urged by Dr. Kennicott, Dissertation I., p. 55, etc.; and see the Var. Lect. of De Rossi on this place."
NET Bible note: "Several ancient textual witnesses, including some LXX MSS and the Vulgate, support the reading “Moses” (מֹשֶׁה, mosheh) here. Many Hebrew MSS have a nun (נ) suspended above the name between the first two letters (מנשׁה), suggesting the name Manasseh (מְנַשֶּׁה, menasheh). This is probably a scribal attempt to protect Moses’ reputation. For discussion, see G. F. Moore, Judges (ICC), 401-2."
Among the translations that back the reading 'Moses' instead of 'Manasseh': ESV, NAB, Einaudi (2023) [Italian], NLT, TOB, Alter, NJB, ASV, NWT(2013), BBE, CEV, Darby, GNB, Douay-Rheims.