All fixed - turns out that initializing your entire mod in afterMapGenBeforeHistorical doesn't work great in game modes that skip over that function entirely. Thank you for the report!

NullReferenceException: Object reference not set to an instance of an object
at WorldNames.Kernel_Names.onTurnStart (Assets.Code.Map map) [0x00001] in <4190aa0bd7ee4922a94fd8014279cab0>:0
at Assets.Code.Map.turnTick () [0x00382] in <067a2752cc9d4478875d589c5ec71a6c>:0
at Assets.Code.World.startup (Assets.Code.GameOptions opts) [0x00749] in <067a2752cc9d4478875d589c5ec71a6c>:0
at Assets.Code.PopupXBoxGodSelectMsg.onClick () [0x00093] in <067a2752cc9d4478875d589c5ec71a6c>:0
at Assets.Code.PopupXScroll.bCancel () [0x00012] in <067a2752cc9d4478875d589c5ec71a6c>:0

Null pointer was thrown during tutorial (1st tutorial). Did not appear during main game normal start up.

Alright, I have a pretty solid theory, and if that theory is correct the crash will be gone.

Oh no D: I can dig into it just knowing it happens on onTurnStart, but a save or seed+settings+mod configuration might speed it along

Doooooppppllisss it broke

ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
at System.Collections.Generic.List`1[T].get_Item (System.Int32 index) [0x00009] in <6073cf49ed704e958b8a66d540dea948>:0
at WorldNames.Kernel_Names.onTurnStart (Assets.Code.Map map) [0x0002b] in <4c8d8747c3f14b0dbf85404f72a17785>:0
at Assets.Code.Map.turnTick () [0x00382] in <9a5a99be31474a10ab5a4f72ac2f88ac>:0
at Assets.Code.World.startup (Assets.Code.GameOptions opts) [0x003c4] in <9a5a99be31474a10ab5a4f72ac2f88ac>:0
at Assets.Code.PopupGameOptions.startGame () [0x0001f] in <9a5a99be31474a10ab5a4f72ac2f88ac>:0
at UnityEngine.Events.InvokableCall.Invoke () [0x00010] in <b18ae20108aa49ccb481b7d86c1fcbd2>:0
...

I do in fact enjoy talking about modding this game, both the technical side and the design side. :D

Person.getPortrait works by checking the person's society, checking if it has a unique portrait list, pulling something from it if so, and pulling something from the species' portrait list if not. Basing it on the original portrait actually solves a lot of the problems now that you mention it, but a Person doesn't actually have an "original society" property to store it in. I suppose the cleanest method would be to store a list of each person's starting cultures in the mod's core, then using a special overriding library to change Person.getPortrait to something else entirely, which is actually totally feasible.

I'm still not doing it for this mod, though, for reasons I hope will become clear in the coming months.

Don't bend over backwards to fullfill the wishes of the workshop lol, the mod is absolutely fine as it is.

If they change society, maybe they could keep the portrait? Base their portrait on their hometown, on the moment they "spawn"?

I might be just saying nonsense, no idea how this works behind the scenes. But if such thing is possible, it would be pretty good at having each society look more distinct.

It's kind of pushing the bounds of possible. Societies can include unique portrait lists, but cultures can't, and in the base game societies don't really have an assigned culture. This can theoretically be handled by making each culture its own type of society (or by overriding a bunch of the base game code directly), but this approach has major risks of stepping on other mods' toes and I suspect would also make the game run slower.

Even once that's overcome (which I might be doing anyway for an unrelated mod), there's a risk of messing things up if the heroes change societies. I think I'd need to either make society changes impossible (which poses compatibility risks with other mods) or give each of them their own portrait list of the same length with portraits in the same spot for each society having the same skin/hair/eye colours (which would also conflict with any base game portrait mods).

I wonder if it's possible to make that every culture has it's own pool of portraits associated with it.

This mod is great. it actually makes a ton of difference in making the worlds feel more real; when the names are unique and have meaning, they stand out more, characters become more recognisable. Great mod.