I am 100% sure that this method had to work.
I used this script:
local StarterGui = game:GetService('StarterGui') StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Chat, false)
It is a LocalScript inside StarterGui. I want to disable chat because i use custom chat provided by Admin Script, but whenever i say something in chat, both custom bubble chat, both default bubble chat appears!
Chat bubbles don't care about SetCoreGuiEnabled. Go to your place settings and use "Classic chat only". That'll hide bubbles and show chat in the default chat gui. (Which you've hidden using SetCoreGuiEnabled)