The primary resource for learning about the lore of Outward is through Transcripts of in-game dialogue and writing. All lore information on the Wiki is verified by referring to the transcripts.
List of Lore Articles
Characters and Factions
Some of the Unknown Arena boss-fights, while not technically "canon" to the story, contain hints towards different lore elements:
Prior to Outward's release, a number of "lore letters" were shared with the community which give background information on the factions, characters and locations of Aurai.