We can say he was from Thrace, that he was captured as a slave and fought as a gladiator in Capua, he led a slave revolt, and ran the Roman Army ragged all over the Italian peninsula. Including armies led by Marcus Crassus and Julius Caesar.

We can say that Jesus was from Nazareth, he started a weird little apocalyptic group within Judaism when he was around 30 years old, was baptized by a guy who started a parallel apocalyptic group (there were a lot of these guys running around Israel at the time), and he was crucified by the Romans. He almost certainly wasn't trying to start a whole new religion separate from Judaism; that came later, likely with Paul.

And that's it, that's the claim. Nobody is asking you to believe in the superstitious aspects, just the completely mundane claim that Christianity likely has a singular individual that inspired the movement.