Arcane is officially League of Legends canon now, according to Riot

I like the article's optimism that things that contradict the new canon will eventually get worked out. The last time I played, characters still had voice lines referencing summoners years after summoners (and the entire concept of the League) had been written out of the lore.

As much as I hate riot the show was pretty good. It had real potential to be amazing if they weren't afraid to add more episodes to the first season (as is so often the case these days). But good nonetheless