Canonically, Ranboo’s age has not been explicitly stated in the Dream SMP lore. However, based on the information we have, we can make an educated guess about his age.
Fundy’s age progression gives us a timeline reference. From the start to the current events of the SMP, Fundy has aged from 8 to 16. This implies that at least 8 in-game years have passed. Tommy, another prominent character, is referred to as 16 in-game. Tubbo, who is known to be older than Tommy, is around 17 years old.
Given that Ranboo is a contemporary of Tommy and Tubbo, it is reasonable to assume that he is also around the same age. Therefore, it is likely that Ranboo is canonically around 17 years old.
It is worth noting that the ages of characters in the Dream SMP can be somewhat fluid and subject to interpretation. The lore and character development are shaped by the creators and streamers, and they may introduce new storylines or details that could potentially change the ages of the characters. So, while we can make an educated guess based on the available information, it is always possible for the canon to evolve and bring new surprises.
Based on the information we have, it is reasonable to assume that Ranboo is around 17 years old canonically in the Dream SMP.