If the question is about how do I handle the problem personally, I always try to minimize my usage of the word "that" in order to avoid these instances altogether.
"That bike that is blue" becomes "the bike which is blue" or simply, "the blue bike." Therefore: "That that is blue" becomes "that which is blue" or even "what is blue" in some contexts.
"I know that it is true" becomes "I know it is true." I simply omit the word "that" and it still works.
"That that is true" becomes "That which is true" or simply, "The truth."
I do this not because it is grammatically incorrect, but because it is more aesthetically pleasing. The overuse of the word "that" is a hallmark of lazy speech. Indeed, if avoiding these instances causes you to think outside the box, your speech and writing will become more fresh and creative as a result.
To clarify, I don't go out of my way to avoid the word "that." I simply reduce my daily usage of it in order to avoid confusion.