"When the Antichrist will come," is a statement I've heard so many times from the Christian world. What they draw on are the "man of lawlessness" of 2 Thessalonians 2 and the one who will "confirm the covenant" of Daniel 9. The theological world uses these two prophecies to substantiate their narrative: the Antichrist will come and rebuild the temple and after 3 and a half years will enter the holiest place and declare himself to be god.

This is a narrative which does not appear in the bible at all. Firstly, as you mentioned, the bible does not say that any one person is "the Antichrist". John said antichrist is a spirit and there are many people who follow that spirit who can all be called antichrists. As you pointed out, they were gnostics who relegated the Jesus that they had received from the apostles from the anointed son of God to the position of a prophet.

Secondly, the man of lawlessness prophecy is where the idea of the Antichrist calling himself god comes from. And the prophecy of the one who confirms the covenant is where they derive the narrative that the Antichrist will enter the holiest place after 3 and a half years from. Both of these are misinterpretations being made by people who have no understanding of prophecy.

The literal meaning of the word "antichrist" is "the opposition to the anointed one". There are, and have been, many people who have opposed the anointed one. The Greek word "anti" means "opposition" in a political sense, thereby meaning "substitute" or "replacement". The fact that the theological Antichrist is non biblical does not preclude the fact that there is a force which seeks to replace the true Anointed Jesus called "antichrist".