Unfortunately it's kinda up in the air what lore is or isn't cannon.
We know that anything that has come out since the Shurima patch is cannon (which is like 1% of the lore), but almost everything that came before may not fit with the new lore yet, and may be subject to retcons at any time.
It's a shame, but it's probably a smart idea not to let yourself get too invested in any of LoL lore for a while, because most of it is probably going to get changed pretty soon.
It seems like Riot's plan is probably to make multiple events take place in different regions of Runeterra, and to retcon each champion into belonging to one of those regions.
In my opinion, it's kinda boring not to have a place like the Institute of War where champions from different parts of Runeterra can believably interact.
How are we going to get stories about Blitzcranks dating service now? What about Morgana's bakery?
I could be wrong, but to me, Riot seems to be trying to commercialize their game.
It's lore is losing the charm and scope that it had before.
To me at least, it's becoming boring and generic, which is such a shame considering the potential that it had.