Good day Arcanamoon,
Yes, there is a way to alter the End/Discard Phase. The Hand Discard actually happens at the Turn Start for the Party, so if you don't want the Hand discarded you can edit the Turn Start parameters in CGC Core Engine and remove the Eval that does the Discard before the cards are drawn by the following Eval. In the Blank Templates, you'll see that it is a lot simpler and we use the Card Action "Discard Until 0" at Turn Start, that can just be removed to have more traditional card gameplay. We cover this exact topic in our tutorial video about Card Actions.
And yes, plugin updates will go across all platforms we make our plugins available. For Steam, there will be a slight delay as GGG needs to localize new content we add to Japanese and once that's done will be part of the following month's update to RPG Maker MV & MZ.