Here's my attempt at an endings guide. I'm sure there are other ways of getting each ending than what I wrote, especially where Maddie is concerned as I didn't focus much on her routes. If I have something wrong or missing some details, people can let me know and I will fill them in.
Ending A: Get Nora to let Rion come with you to the portal or follow Maddie's path and don't be evil. When you're posessed/contacted by Anubis, accept his offer. I think you need lust of at least 6 with the girl or evil of at least 2.
Ending B: Be as evil as you can. Take the stone and meet Tal when you have the chance. Deepthroat her. Don't let her leave. In the temple after the Anubis statues puzzle, tell the girls to stay away. Don't release Bastet/Neferatri, continue and make her pay. At the portal, choose to crush Anubis.
Ending D: Convince Nora to let Rion come with you to the portal. Refuse Anubis's Deal. Or follow Maddie's path and don't be evil, then refuse the deal.
Ending E: Be evil as with ending B but choose to accept Anubis's deal
Ending F, Maddie Special Ending : Special ending on Maddie's path. At the entrance area to the portal when you have a chance to shoot or not, don't shoot. Stay hidden rather than yelling out to Nora. When you're posessed/contacted by Anubis, think of Maddie and fight back. Don't cross the gate.
Ending L, Rion Special Ending: Rion solo path. Convince Nora to let Rion and MC return to Aswan instead of going to the Portal.
Ending S, Nora Special Ending: Nora solo path. At the portal, try to wake Nora up (need romance of at least 6), then protect Nora from the stone (need romance of at least 8).
Ending T, Nora and Rion Special Ending: Rion and Nora threesome path. Get Rion affinity until you can start getting Nora affinity (joke about proposing to Nora is the first I think). Then balance Nora and Rion. Then you need "Rion & Nora" points. You can get those by doing the following: NOT interfering when the truck breaks down and Rion gets confronted by the two men, saying you understand Rion's attraction to Nora while you're in the back of the truck (need 1 romance with Rion to get to that option), and repeatedly attacking Nora's area during volleyball. I don't think you need all of them, I think it's actually just important you don't be so far committed to one path that you get Rion or Nora's solo scene in the tent at the oasis. Then convince Nora to give up her mission and leave with MC and Rion. It's not difficult at all to get this one, I'm just not sure the exact minimum requirements.
Ending M, Maddie Main Ending: Maddie's main solo path. Same as F but choose to cross the gate.
Ending N, Nora Main Ending: Same as S but cross through the portal instead of protecting Nora from the Stone.
Ending R, Rion Main Ending: Be on Rion's path. Convince Nora to let Rion come with you to the portal. When you're posessed/contacted by Anubis, think of Rion and fight back.