In MT 1 Sam 1:11, Hannah vows to YHWH that a razor would never touch her son’s head (should YHWH give her a son). But the LXX (1 Kgdms 1:11) contains a plus: that her son would never drink wine or strong drink.
And she vowed a vow and said, “O LORD of hosts, if you will indeed look on the affliction of your servant and remember me and not forget your servant, but will give to your servant a son, then I will give him to the LORD all the days of his life, and no razor shall touch his head.” (ESV)
…and vowed a vow to the Lord, saying: “Adonai, Lord, Eloai, Sabaoth, if looking you will look on the humiliation of your slave and remember me and give to your slave an offspring of men, and I will give him as one devoted before you until the day of his death, and wine and strong drink he shall not drink, and no iron shall come upon his head.” (NETS)
I always thought that the LXX represented an updating of the proto-MT: the translator was explicitly associating Samuel with the previous judge (Samson) by filling in the gap and making Samuel a full nazir from conception (per Num 6, Jdg 13). At face value, it seems more likely that the bit about abstaining from alcohol would be added rather than omitted (if the MT were later).
But what if the LXX represents the earlier reading, and the MT did omit the part about alcohol in order to accommodate Samuel’s priestly role throughout his prophetic/judge administration? Priests regularly used alcohol for drink offerings (Lev 23, Num 28-29), though they are never expressly commanded to drink any portion of the offering. Also, 1 Sam never says explicitly that Samuel drank or administered a drink offering.
To further complicate both of these suggestions: If in the LXX Samuel was to be a full nazir from conception like Samson, then it would be strange for the LXX to have added to 1:18 that Hannah subsequently ate “and drank” in her quarters. On the other hand, this is before Samuel is conceived (1:19-20).
Alternatively, what if the MT removed the reference to strong drink in order to make Samuel not a nazir because he was frequently near dead bodies during his tenure? He went to war (1 Sam 7) and hacked Agag to pieces (1 Sam 15).