Yes.
Except for the one official, established case of a minor voluntarily joining the Russian forces and being killed in combat—he was 16 years old—there are a lot of established cases of teenagers who are, happily, still alive, but they are trained in military programs.
Using children directly as soldiers is not the only way Russia is using children for war purposes. There are also known cases of Russian authorities using children from the occupied territory for intelligence purposes to gather information. They also make teenagers patrol the territory and bring information on people who have links or connections with the Ukrainian armed forces or the Ukrainian law enforcement authorities.
We also know of cases, officially established, in which Ukrainian children unknowingly provided data by locating objects through a mobile game developed and launched by a pro-Russian IT company that is controlled by the Russian special services. The children didn't know that by playing this game and by getting virtual awards and virtual money for uploading the photos of the objects, they were providing data for future missile attacks.
The range of Russia's methods of using children for military purposes is very broad. It's not only the direct use of them as soldiers.