Riot Games Black Friday Deals most likely won't be found. Historically, Riot has never offered any deals for their games on Black Friday. If you're looking for Black Friday Deals from Riot, you won't get any.
Riot Games Black Friday Deals: Are There Any?
Riot Games makes free to play games, so there's not much deal you can cut from free. Their in-game stores only have cosmetics and premium currency, and it's unlikely those will feature a cut in prices.
The most we might get to see is an in-game event celebrating Thanksgiving in League of Legends or Valorant. They also have never done anything like that before, so don't get your hopes up. Riot Games' Black Friday offerings will be sparse if any.
If you want some freebies in some of Riot Games' offerings, you can check out Twitch Gaming to earn some Skin Shards in League of Legends. At the very least, you can reroll to get the Skins you want.
Sometimes, you have to make your own luck. In this case, you'll have to make your own deals.