I have a case where the desktop and mobile layouts are very different: having a few container boxes makes desktop version easy (a couple of vertical flex boxes

I have a case where the desktop and mobile layouts are very different: having a few container boxes makes desktop version easy (a couple of vertical flex boxes with content) but on mobile everything is flattened into a single box, and everything has a different sorting order than on desktop. display-contents makes this simple. The Javascript workaround for MSIE11 is not so nice.