Skaar's age in the MCU is estimated by She-Hulk Concept Artist.
The concept artist for She-Hulk: Attorney at Law commented on Skaar's look in a post on Instagram.
More significantly, during the season finale, Constantine Sekeris provided us an estimate of the character's age.
Given that the Hulk just got to Sakaar roughly ten years ago, Sereki's assertion simply serves to further confuse the issue of Skaar's age.
Sekeri could be mistaken, or perhaps time doesn't flow the same way in Sakaar.
The MCU is now more focused on other characters since She-Hulk finished, therefore we won't learn anything more about Skaar for a long.