Now that I think of it Princess Ruto from OoT is talked about in the Zora lore in the Domain text walls in this game. There was something about how she helped the hero of that time and Zoras honor her to this day etc. This would imply an adult or downfall timeline then? This fact would rule out...
Adult or child timeline would not make sense because it is said how Ganon has come to attack Hyrule many times. The only timeline where this is the case would be the downfall one. That said if it were child or adult timeline it would have to be waaaaaay into the future. It's more than likely...