According to this
https://xcom.fandom.com/wiki/Commander
Twice
The Commander does not take to the field personally in most scenarios, only being seen on the field twice, the first during the Tutorial, and the second during the final mission, where they psionically control an Avatar to lead the final combat mission of XCOM 2, Operation Leviathan.
Of course, the commander is ourselves. I do not remember seeing the commander in the tutorial and final mission.
Where is it?
Any screenshot?