HoMM VII Haven Units – Haven faction units from the seventh installment of Heroes of Might and Magic.

What if you simply program the movement along a line? As an additional effect. Like if the model didn't have a movement animation, and it would freeze, spreading its arms and legs, and slowly float in the desired direction. Here, it would be the same, but the model would flail its arms and legs in the air, and you could adjust the speed to make it look more or less like it's moving on its own.

Added 1 minute ago
I just understood that it's possible because I read about something similar in the thread about creating new heroes (they were discussing the movement of Kha-Belekh, and there was a situation where a portal animation appeared around him, and he himself floated motionless along the path of movement).