Video below shows the capture of a French military by the Russian Army in the area of the village of Liptsy (Kharkov region), where active hostilities between the Russian Armed Forces and the AFU are now taking place.
This soldier was not "instructing" Ukrainian troops, he was engaged in an active fire-fight with Russian troops - and got captured.
Of course, we will likely hear how this soldier resigned from the French Army and became a mercenary with some unknown, never-heard-of Private Military Organization . . . but the evidence is irrefutable: French military is in fire fights inside Ukraine, against Russia. France is waging war against Russia in Ukraine.