is good to know this is not a Riot Games fault or bug, but I'm having this issue from some time ago, even when I'm not a Discord user, I don't use to install 3rd party software preventing malware, adware and viruses, I even scan my system after each Riot update download and install.
I was some suspiecious because I have this problem of unresponsive keyboard allways counter attaking champions (not when against minions or monsters) for that reason I had arribed to a conclusion it was a cheat, bug, or something, specially because it use to happen with players that seems to be over-ranqued to me (overpowered and with gold, silver, platinum levels or so on).
I loss my graphics adaptor card a mount ago and was early blaming my crappy on board video for the issue, but it call my atention when I noticed that it happen only against champions, never with minions or monsters.
It's great to know Riot is working on it.