how to "self mute"
step 1. download autohotkey https://autohotkey.com/
step 2. create the following script
#ifwinactive League of Legends (TM) Client *Enter::return *NumpadEnter::return
step 3. keep said script loaded
step 4. go into your config file and find the text that says "chatscale" set the number next to it to -150 if the text isnt there. load a custom game. and edit chat scaling. it will force it to appear. do the same with "persisted settings"
congratulations. you have successfully 100% disabled in game chat. you can also "pop into chat" to see if you need to report anyone by clicking the chat scaling bar and then pressing cancel