I think I've found a direction to go in that fanfic I keep talking about.
I'm not either clever enough or patient enough to come up with a new mythology of the Stargate universe that is consistent with what was shown on screen but also isn't insulting to the real worlds of history and archaeology (physics will have to fend for itself). I'm also unwilling to go too far off canon.
But even as I risk turning the story polemical as I trot out straw dogs (assuming straw dogs trot), I think it may work to bring in some of the large body of Ancient Astronaut and associated theories and treat them as the hogwash they are.
In fact, I'm looking now at doing a bit of a Foucalt's Pendulum trick (always steal from the best). Lara plays along with the treasure-hunting team of "L. Lytton Peabody" in a barely-legal exploration of something a lot like Watson Brake; earthen mound systems built by early indigenous cultures of North America. Peabody has lots of theories about Vikings and Lost Tribes of Israel and the usual roster of "Anyone but Native Americans" of the alternative history crowd, and perhaps due to his tireless self-publicity or perhaps his far-right political connections he's at least attracted half an eye of attention from the NID.
He may not know who the girl with the charming accent he found at a local diner is, but the NID does, and they have a task for an adventurer-archaeologist. Possibly (probably?) off-world.
I don't know yet why she is in Mississippi or Louisiana (prime Mound Builder sites) but I have been looking at Lafcaido Hearn, who before Kwaiden was writing about (and living in) New Orleans, and was friends with a particular famous practitioner of voudon.
So at least I get to write about something I have some interest in and information thereof. Unfortunately, although I'd love to do more with the fish-out-of-water of our British peer and heiress slumming in truck-stop towns in Middle America, my personal memories of traveling the same blue highways are out of date even for the period I'm setting the fanfiction in.
And this doesn't get me much closer to the next chapter, as even if I don't start (as I really want to) in media res, I want to cut away from Lara Croft and let the SG1 crowd struggle along alone for a while. Obviously, there's a briefing room scene to be had where Daniel can pontificate about Akhenaten (and Djoser, and Imhotep, and so on). And I'm willing to give him the credit to be re-thinking his own "Pyramids were built by aliens thousands of years earlier than anyone thinks" ideas.
But that's not where I'm going, as much as the Valley of Kings or pretty much any part of ancient Egypt is attractive. So I sort of need to get him out to Abingdon where Lara's aides and name-drop Atlantis on him and send him off on a largely-mistaken tangent.
Of course in-universe Daniel does eventually discover Atlantis. Yeah, that's Stargate for you. But that doesn't mean that Blavatsky was right or that Mu exists or that Atlantis ever fought the Athenian Republic... So there's plenty of room for Daniel to actually get something wrong for a change. As long as I can manage to gather everyone together at Mount Shasta to play with a merely-dormant volcano and some inconvenient ancient technology while the very-real Norse Frost Giants attack...