I want to know the answer to the following question:
What does rendering software display when it can't process a Unicode character?
All the background I'm provided with is that "The Apple's Last Resort font will display a substitute glyph indicating the Unicode range of the character, and the SIL International's Unicode Fallback font will display a box showing the hexadecimal scalar value of the character.". Is that enough to answer the question?
Answer: no