How do I report boosters

If you have 100% evidence of someone playing on someone else’s account - regardless of if it’s boosting or not, you can submit it in a support ticket under “I’d like to report abuse”.

If they aren’t playing on someone else’s account but just duo queueing together, that’s not against the rules.

You don't.

Under cheating in the post game screen is fine.

But if you feel uncertain, then submit a ticket as Chermorg mentions.

Submit a ticket on League's support website. It's a waste of time though since Riot only bans people for saying things in the chat box, not for actually ruining the game.

Been seeing a lot of boosters and still waiting on the ban hammers or unless rito does not tell you anymore if someone gets punished... If that's the case then there is no point in reporting....

I'd be willing to bet the next banwave will be around the same time end of season rewards go out. Better to take them out when they can't destroy other people's rewards through an 'I'm going to take them with me attitude'.