No, actually I think the letter referred to in 2 Thess 2:2 might be 2 Tim, which I do strongly think was written by Paul, but was the last one written, so 2 Thess may be more like a decade or two after his death.

But I also think the archetype of 2 Thess 2 is largely a tradition coming from Paul in how it mirrors his own language around being lawless (1 Cor 9:20), about using signs and wonders to convert (2 Cor 12:12), his insistences he’s not lying and the contemporary allegations he was doing evil in the name of good. 2 Thess 2 in many ways reads like Paul’s guilt or self-awareness in his actions opposing the pre-Pauline Jesus movement are being projected as a warning to his followers of what to look out for in who might come next to apply the same methods to his own tradition.

Much like how the Corinthian Creed may have in its core predated Paul, I think the warning of the lawless one that will set themselves up in the church predated the letter and reflects Paul himself.

We are in agreement that the one he was fighting was a proto-gnostic one.

But ‘proto-gnostic’ is a meaningless term invented in the last 20 years after the realization that ideas previously labeled as 2nd century Gnostic predated that and were missing key features of later beliefs.

When you dig into the proto-gnostic tradition’s development, you’ll see an influence of Epicureanism - specifically Leucretius.

For example, Leucretius described the development of life in naturalist terms as the smallest seeds scattered randomly where only what survived to reproduce multiplied. He even used the language of “seed falling by the wayside of a path” to describe failed biological reproduction. And this was all 50 years before Jesus was born in a poem very popular in the Roman empire.

You see that exact same language and concept in the sower parable.

Which is the only parable in Luke and Mark which is spoken publicly but then given a “secret explanation” to the apostles of Paul’s church in private.

Paul actually first refers to sown seeds in referring to the human body in 1 Cor 15, similar to how the sower parable is placed in the surviving proto-gnostic text right after a parable about how the human being was inevitable no matter if lion ate man or man ate lion because the human being was like a large fish selected from many small fish.

In that same part, Paul refers to a first and second Adam, which was a core belief of the later tradition surrounding that proto-gnostic text. It’s also a section that scholars have said seems to be arguing with Epicurean ideas.

It’s only in 2 Corinthians that Paul is again talking about sown seeds as being related to proselytizing efforts (similar to the “secret explanation”), after chiding the Corinthians for their beliefs in a different version of Jesus.

The proto-gnostic version was closer to representing the original ministry pre-Paul than the canonical one after.

You can even see how 2 Tim 2:18 complains about the over-realized eschatology found in proto-gnosticism and then how 2 Thess 2:2 is warning against believing in the authenticity of a letter from Paul mentioning any over-realized eschatology.

That over-realized eschatology makes a lot of sense in the context of the proto-gnostic beliefs which extended Epicurean naturalism by modifying its concepts of eternal recurrence to argue for the existence of an afterlife even if the origins of the world were naturally occurring.

But it was a death knell for the authority of a priest class and the industry of organized religion. So suddenly Paul came along falsely telling people the end was any minute, that he deserved to make a living off telling them that, and that salvation was conditional on obedience and servitude to the church as opposed to the pre-existing belief in Corinth that “everything is permissible” (a very Epicurean concept, along with things like communal eating).