In this case, slower = better. Jets have a hard time shooting down drones because most drones fly slowly. The Yak has an extremely slow stall speed.
Also, the weapon of choice is a machine gun, which is very cheap to use. Fire 1000 rounds at a drone to kill it and you get a $500 victory. Fire a missile at it and you get a $50-100,000 victory.
And BTW if you can get the Ukrainian AF to divert itself to acquiring and training for the slow prop plane counter cheap drone mission you have been effective in distracting the enemy.
If you want low and slow try a Nazi-era Storch.