Acts 25:8 ESV “Paul argued in his defense, “Neither against the law of the Jews, nor against the temple, nor against Caesar have I committed any offense.” ”
Paul claims to be blameless according to Jewish Law and to be respectful of the temple. He does not speak against the temple or the rites practiced there.
Acts 25:19 NET “Rather they had several points of disagreement with him about their own religion and about a man named Jesus who was dead, whom Paul claimed to be alive.”
Here, Festus is describing Paul's case to King Agrippa. Festus sees it as an internal Jewish dispute— a disagreement “about their own religion". Paul apparently looks and acts just like other Jews and there is no sense that he is from a separate religious community.