Okay, great idea! That link I gave for 2 Thess 2 will allow you to see the best Greek copies available. IIRC there is even Hebrew of the Septuagint origins, if that’s your thing. Point being, Jerome was faithful to what the GReek text taught, and he is vindicated in his opinion/translation because it conforms to the verses previous and following, in meaning.
The original word was "apostasia". There's no getting around that no matter what Jerome's credentials are.