It is true that professional fouls can be committed with legs as well as arms. However, by challenging with your legs/feet, you at least have a chance of someone interpreting it as an honest attempt to win the ball. In this case, I thought Ndombele was trying to win the ball, as did the ref. You clearly did not. However, judging by the tone of your reply and your original post, you clearly have a "we was robbed" mindset and so nothing I say will change your opinion. Enjoy the rest of your day.