new-be if bracketed that way is formally identical to Greek neo-phyton, insofar as the reconstruction of Proto-Indo-European (PIE) *bʰuH- holds in either case.
The origin of phyton "child, growth", which should not concern us beyond the basic fact, might reflect PIE *bʰuH-tó (Wodtko et al., Lexikon der indogermanischen Nomina), maybe deverbal from phuo "to grow" (Wiktionary). The fact that Semitic בַּת, بِنْت etc. "daughter" or Sanskrit पुत्री for example are not related to this reconstructed root goes without saying.
Of course, the first question one has to ask pertains to attestation. Douglas Harper dates newbie "by 1969".
Second, word formation might offer a clue about stratification. Harper speaks of an ostensible diminutive suffix, which I have to guess has to be -y-, as Harper's refers further to noob and indicates Military Jargon. This is a bummer because troops are drafted from wherever. The only labial exponent that comes to mind is seen in knob, which has been compared to knave, Old Norse knapi, Dutch knaab, German Knabe etc. Other hypochorisms with -b- that couldn't be secondary (freebie) don't exist to my knowledge.
Third, comparative evidence from languages more closely related than Greek might help. Save for the existential paradigm to be, the cognates from this root seem to cover a lot of ground (op. cit.):
booth, through Old Norse
Old English būr "dwelling, house, store", Dutch bur "farmer", burlap "loin cloth".
Old Norse búi "dweller, inhabitant; neighbour; (law) a neighbour acting as a juror", nábúi "neighbour", whence Scottish Gaellic nàbaidh (Wiktionary).
beam, German Baum "tree", ...
et cetera
German Neubauer, is common as surname, same idea as Newman, Neugebauer, or toponymic New York. Is that it?
The labialization expected from English is enough to explain newie after assimilation from *neuvui. Whereas "b-insertion" (@FF) is not an actual thing (eg. Louis doesn't become lube).
However, since I'd bet that knave is akin to kind, gentle, genius, German Kind "child" etc., which derive from PIE *ǵenh₁- ~ *ǵn̥h₁-, it may be notable that laryngeals are theorized to have had a labial feature (Frederik Hartmann 2021, The phonetic value of the Proto-Indo-European laryngeal.
In: Indo-European Linguistics).
In this case, fortition towards excrescent *-b might be a possibility.