Ukraine has occasionally been sending small numbers of aircraft (both helicopters and fixed wing) to the vicinity of the front lines in the south and west. These forays to support their troops are shot down with some frequency so the forays are becoming less common.
Russian supporting aircraft are operating in these front areas with their losses being rare in recent months. It’s not “air supremacy” but close to it along the front.
Russia has Air Superiority on their side of the line, with certainty.
And they also have the ability to project out to the Ukrainian line, at some risk.
But with Ukraine on the “offensive”, all they have to do is lay back and wait for them.