First some facts:
The previous question on this at Who led the people of Israel out of Egypt in Jude 5? was posed and answered before some of the data below became available.
The following edited editions of the GNT have the reading in Jude 5, "Jesus": NA28, UBS5, THGNT.
All the rest I could find have the reading "Lord" including NA4, NA27, UBS4, Majority Text, W&H, Souter, Byzantine Text, Orthodox Text, TR, NIV, F35, etc. In Metzger's Textual Commentary on UBS4, he regards the textual evidence for "Jesus" as both "weighty" and consistent with "Critical Principles" (Perhaps he disagreed with the committee??)
So, now to the question. If the reading is "Lord" to what does this refer? The title, Kyrios" is certainly used by Jude to refer to Jesus such as v4, 14, 17, 21, 25. He possibly uses it to also refer to the Godhead generally in v9, but this could also be specifically Jesus as well. The same is true of v5.
1 Cor 10:4 is probably a precedent for saying that Jesus is the person who saved Israel out of Egypt. In the rest of the NT, of the approx. 740 occurrences of "kyrios" most often refers to Jesus.
Such a decision is a matter of personal judgement. In view of the above, I believe the evidence is that in Jude 5, if the reading is "Lord" it refers to Jesus.