Well I won, January 1932. It was a good game, one of the most tense I have played. And only my 2nd Immortal win, the first was Bindy's recent challenge (the quick speed AP one with Justinian).
I played as Darius which looks like the popular choice. Barbs on for me again since I play these games just like a normal game.
Mehmed out-REXed me at the beginning and I had no horses or copper

Eventually got some iron and captured a barb city. Built the Great Library without marble in my capital which was a great production city.
Then I just turtled watching everyone dogpiled Mehmed. I joined in when I teched assembly line before anyone else had rifling. I was first to liberalism in 880AD, took astronomy for observatories and trade-bait, I only had one coastal city.
Shaka vassalised Mehmed before I could do much damage although I did take 4 cities from him, 2 coastal.
When I got scientific method I realised I would have to build a junk city near Ankara to flip Mehmed's 2nd source of oil, which took a long time to flip (built a theatre and then just built culture). But flip it did.
I had aluminium too which helped of course.
Late game had to raze one of Brennus' legendary cities with something like a stack of 30 odd marines in transports to prevent him winning. Stupidly he DoW'd Mansa just before then and moved most of his defenders out of the city, he had 45 defenders at one point and if he had kept them in his city he would have won

What a pillock.
At then end I was just hoping Brennus didn't get a Grat Artist to finish off his culture push, but he didn't get one. I landed a large stack of Modern Armour and Mobile Artileery to try and raze another legendary city but that stack was annihilated by endless artillery attacks the turn after it landed
Only other big build was the internet which meant I was tech leader by far in the late game.
Shaka kindly spread Mining Inc to my cities and I founded Sid's Sushi at the end but didn't spread it.
3 golden ages, one from the marathon/snickers event, and 2 more from great people.
I built all the components of the ship my 2nd engine was finished 5 turns before my ironworks city built the life-support.
This was a good gauntlet but took me about 46 hours of gameplay to win
EDIT: Opponents were (lucky dip, I didn't choose the AI):
Mehmed - dogpiled by everyone. Had Sitting Bull as a vassal at that point.
Sitting Bull - vassal first to Mehmed then Shaka. Totally backwards with only 3 or 4 cities.
Shaka - Score leader with vassals Mehmed and Sitting Bull.
Mansa - was pretty backwards too, vassal to Brennus on and off, every time he broke free Brennus seemd to DoW him.
Brennus - 2nd in score, vassals Mansa (most of the time) and Gilgamesh (peaceful vassal)
Gilgamesh - my main trade partner, voluntary vassal to Brennus most of the game.