biblically there’s no evidence that he wasn’t baptized in fact the evidence would lean towards he had been because of this
“Then went out to him Jerusalem, and all Judæa, and all the region round about Jordan, and were baptized of him in Jordan, confessing their sins.”
Matthew 3:5-6
there’s no proof he was among them at the time but there’s no evidence whatsoever that he wasn’t baptized or really that he was. We know he had heard Jesus preaching the kingdom and he believed because he asks to be part of the kingdom when Jesus received his glory
so the thought would be he’s a conscious man who fears god and most likely would have been among those baptized when it says “ ll Jerusalem and the region and Jude’s went and got baptized by John
unless he came along later which again we don’t have any evidence in any way for he was likely among those baptized at the first but there’s simply no conclusive evidence either way certainly nothing to even suggest he wasn’t baptized all we can say is he wasn’t baptized while he was on the cross nothing says he couldn’t have been beforehand nd most likely he was because the whole region was getting baptized