I compared the mod descr_cultures to the vanilla descr_cultures and copied the following into the top of the file:
symbol data/models_strat/residences/symbol.CAS
siege data/models_strat/residences/siege_icon.CAS

blockade data/models_strat/residences/blockade_icon.CAS

I no longer have the original error msg. Instead, a new one that says descr_engines can't be read and CTD at splash screen.
Any help please?

i have this problem too, do you know how to fix it?

Unfortunately not, when looking at the descr_engines file there is a difference between the vanilla file and the mod file, specifically the lines that start with "oultine" that aren't in the mod file.
I feel like it could be the graphics enhancement dlc I installed before this mod. Maybe the mod isn't compatible with it.
But then again, the dlc was released prior to the last update for this mod so I doubt it's that.
The other thing it could be is the latest patch released for the game. Maybe the mod isn't compatible with that.
Hopefully someone from the mod will see this discussion and offer some guidance for us.

Alright just saw this discussion, I believe your issue might be caused by not playing the game in english, if that's not the case join the discord and explain the issue in greater detail