I do not know personally about this one. But some time ago i wrote my own version: https://boards.na.leagueoflegends.com/en/c/player-behavior-moderation/F59hE5io-self-mute-option
This is a little bit more complicated to set up, but you just have to start it once, before you start playing and kill it from task manager if you want to stop it. This works only for INGAME, not in lobby, so you can write stuff in the pre and post-game part (but you can extend it anytime if you want to).
In theory this should not be detectable by Rito, but i can not guarantee anything. I shared a source so nobody can accuse me with spreading malware.
Hope it helps!