This is an incorrect claim. Based on the research I have done King Charles lll is still alive. Although in January 2024 he underwent a producer to deal with an enlarged prostate. He is still healthy and alive at 75 years old. Spreading false information can not only confuse others but it can also harm the person you are spreading this disinformation about.
https://www.britannica.com/biography/Charles-III-king-of-the-United-Kingdom