public override bool CanApplyStyle( 
   StyleItem styleItem
)

//Run within QueuedTask context.
//Get the Style project items in the project
var styleProjectItems = Project.Current?.GetItems<StyleProjectItem>();
//Get the ArcGIS 2D Style Project Item
var styleProjectItem = 
styleProjectItems.OfType<StyleProjectItem>().FirstOrDefault(s => s.Name == "ArcGIS 2D");
if (styleProjectItem == null) return;
//Get the north arrow style item you need
var pointStyleItem = 
styleProjectItem.SearchSymbols(StyleItemType.PointSymbol, "Circle 3").FirstOrDefault();
if (pointStyleItem == null) return;
//Select a North arrow layout element
var layoutPointElement = layout.GetSelectedElements().FirstOrDefault();
if (layoutPointElement != null && layoutPointElement is GraphicElement ge)
{
  if (layoutPointElement.CanApplyStyle(pointStyleItem))
  {
    //The magic happens here
    //for Graphic Elements such as Point, Lines, Polys, text, preserve size.           
    ge.ApplyStyle(pointStyleItem, true); 
  }
}