I like to imagine that the reason we dont see the sort of indepth lore we encountered in Murkmire in Shadowfen. Is because Shadowfen is now the home of many previously enslaved Argonians. These are people that were born and grew up as someone elses property and were only given some cursory understanding of their own peoples culture and beliefs. But things like Tribes and such was kind of foreign to their situation. So once freed, they formed these makeshift tribes that didnt really reflect the traditional tribes youd be more likely to find deeper into Argonia. And so these groups are still trying to find their own identity and because of this theres not much to say about it to outsiders like those in Murkmire might be willing to share.

I think there may be a clue to some tribe names in place names, the clearest possibility being Sunscale Strand. If the players had access to a more complete Jel lexicon it might then be possible to identify more.