This is up on 'zon prime, and written by Jerome Bixby, who (very relevantly) wrote the Star Trek TOS episode Requiem for Methuselah.
An apparently 30-something history professor (David Lee Smith) is leaving his job and town, and a few colleagues and friends (hey, the asshole biker professor is William Katt! He looks like shit 30 years since I last saw him, but he's still alive!) show up for a going-away party. They notice some oddities in his furnishings, and he tells them a story, that he's a 14,000 year old caveman, and the things he's seen, people he's met. They react with incredulity, get a shrink in…
The entire thing is shot in and just outside a little cabin, with a fireplace. Mostly one-camera, calm, long shots, actors mostly in character and reacting appropriately. I could wish for them to all speak a little more Howard Hawks, New Yorker speed instead of slow and laconic, I don't buy that some of these people are professors, but you work with what you can get on indie flicks.
The writing's not fantastic; he does question & answer, with often terse answers, not technical or detailed, and often interrupted by snarky people. There's one or two, where he's recalling scenery or people, that get something like actual SF writing. What I would like is long monologues about his people, about life in Sumeria, or Rome, or Paris. There's a Poul Anderson book, The Boat of a Million Years which covers a similar character, which has much longer expositions of the nature of living forever.
He has a story of meeting another unnamed immortal, which he puts in the 17th Century. It might possibly be a reference to Le Comte de Saint Germain, a reputed immortal and courtier, though he did eventually die. This is the kind of detail that would've improved the story.
And then there's a religious argument, with a devout true believer, because apparently one random decade in the Mideast 2000 years ago is more important than the other 14,000 years. I think this argument scene is defective in a few ways. First, the believer thinks the King James Version is a "recent" and "accurate" Bible, when in reality it's 400 years out of date and a known shitty translation, most modern Protestants (the theist here is openly anti-Catholic, which is hilarious if you're screaming "blasphemy!" at someone; a "religion" that splits into reformations every couple years is obviously not divinely inspired) use the New International Version, New Living Translation, or New American Standard Bible (for hardcore Hebrew, Aramaic, Greek literalists). I mostly quote KJV because it's poetic and used in so much English literature of the last 400 years, but I'm absolutely not trying to receive "truth" from it.
And while the voices of reason in the room explain the places where Christianity is copied from prior less-shitty religions, the theist is only capable of denying and crying, can't make any rational arguments. SIGH. Look, I'm an aggressive, mocking atheist, but we should be better about presenting the opposition argument than the Christian God's Not Dead idiots.
But I do like his 100-word New New Testament better than anything Christians have ever written in the last 2000 years. They would all be massively improved by switching to this belief.
There is a sequel, Man From Earth: Holocene, written by the director of the first with no input from Jerome Bixby who was by this time dead, and the comments are harsh: "I've just finished watching Man From Earth: Holocene and this is less a review than a warning." Well. Maybe if I'm angry at myself I'll watch that for punishment.
There's also a movie on Netflix, He Never Died, starring Henry Rollins(!!!), about another immortal, though it's more religious/magical, if played for… not comedy, but funny horror? ★★★★☆ for that.