I assume Rashif as Gatekeepr would know. Blackstaff might as well. Rashid says the White Council only knows as much as it needs to. Aand that theres paperwork for coming back from the dead.
On the one hand, Rashid knows way too much.
On the other hand, how does the Oblivion War cross his path? It is about locking things away from Earth in the Nevernever, not about (so far as I can tell) locking things Outside. It seems greedy to make him also the Senior Councillor to know the truth about the Oblivion War and the Archive.
More importantly - we know the White Council SOP is the wrong counter for the Oblivion War even as it's great for diffusing dangerous rituals. I think anyone in the Council who knows can't be so solidly in power as the Gatekeeper or Merlin. Ebenezar? Maybe. Martha Liberty or Eldest Mai? Certainly possible, if more unlikely (Martha is supposedly about knowledge gathering). But the Merlin or Gatekeeper? They seem too big to know the Oblivion War and yet do the wrong thing.
As to who knows of the Archive's role; I would say the Angels are indeed good candidates (or at least intel people Uriel and Anduriel; does Michael have a need-to-know? Or even a need-to-consider, since he probably has Intellectus), but apart from that it's going to be a VERY short list. I suspect Anduriel hasn't told Nicodemus why the Archive was such a good candidate (because Nic becomes rather obsolete if Anduriel has his claws in the Archive). For all we know Anduriel whispered in the old Archive's ear to commit suicide.
The Fae probably know of the War, or the Grimm move would be strange, but they seem too vicious to not strike back if they found a specific target like the Archive. So if any of them know, Odin/Kringle and the Mothers seem the only reasonable ones.
Or, of course, one of the Fae started it, so Mab thought 'humm, our Archive is going after me, but I know how this works'.
Lara and Thomas seem to not know the Archive, so in general I would exclude the Vampire Courts; if anyone would know, it'd be in papa Raith's library (or his mind, and Lara has access to both).
From there we only know a handful; Dragons or Drakul? Possible, but no specifics. Old Greek gods? Athena could easily be one of the sources of the Fae (so see there) but otherwise would likely know, Hades has other things to do, most of the rest is too frivolous or aggressive (unless, as above, Hermes is now Odin). Maybe Apollo, as the god of the Pythia and other seers (though Gaia may have been the first worshipped at Delphi).
And of course, there's a sponsor. Of the people given who know, Uriel and Odin seem the most logical, but the matrilinear linkage suggests a female source to me (though Uriel could undoubtedly be counted as female if need be, the showings so far have been male, and we know from the Fallen that Angels do have gendered tendencies).
So who, then?
Of the maybe candidates given, I do quite like Athena; she fits as goddess of wisdom, and if her essence went into the Archive Ivy would be resurrecting an old part of her by patronizing Harry the Hero (and in the Odyssey, Athena is also often confined to giving advice from afar, rather than intervening directly). According to pre-classical analysis 'Athena' may just be the Athenian representative (and eventually name-giver) of a more general 'city goddess', and of course the Archive has a bit of sense of human civilization against the rest, quite fitting for a city goddess.