From a Jain perspective:

• Jainism is considered one of the oldest living Dharmic traditions. It holds that the path of a liberated soul (moksha) has existed since ancient times and that 24 Tirthankaras (spiritual teachers) have shown the eternal Dharma in different ages.
• Historically, Jain scriptures and temples point to very ancient origins, with Rishabhanatha (Adinath) often described as the first Tirthankara and the tradition going back many millennia.
• In common historical terms, the earliest recorded references to Jainism in inscriptions and texts appear in the centuries around 6th century BCE and later. However, Jains believe the dharma itself is eternal and timeless, beyond a single historical starting point.
• The claim of “the oldest religion” is not universally agreed upon, because many ancient faith traditions (like Hinduism, Judaism, Zoroastrianism, etc.) also trace roots far back in history and have their own traditional timelines.

If you’d like, I can explain how Digambara and Śvetāmbara traditions view the chronology and who they identify as the earliest Tirthankaras, in simple terms.