Was reading up on the newest Destiny 2 patch, and saw that cross platform play was finally available.
My daughter plays via Steam, and I on Xbox. After adding each other as friends, I was able to join her as if she was another Xbox player. The only downside so far is the lack of cross platform voice chat. Fortunately we are near each other, and can yell :-P
Next, we are going to see if it will allow a three way party between xcloud, Xbox , and Steam.