Even in 390 CE, people knew that Celts, Germans, Slavs, Romans, or Greeks were not the real Jews or the lost tribes of Israel. And we’re talking about a Roman Emperor - a man who received the best education possible at the time.
He made good points and had an interesting way of criticizing the Bible and proving it to be man-made, different from the usual takes you hear on X.
There are only 50 pages and it’s just $6. If you’re anti-Abrahamic, you should definitely read it.