Hide all pinned apps and all apps added to Start in Windows 10 1809

LayoutModification.xml

<?xml version="1.0" encoding="utf-8"?>
<LayoutModificationTemplate
    xmlns="http://schemas.microsoft.com/Start/2014/LayoutModification"
    xmlns:defaultlayout="http://schemas.microsoft.com/Start/2014/FullDefaultLayout"
    xmlns:start="http://schemas.microsoft.com/Start/2014/StartLayout"
    xmlns:taskbar="http://schemas.microsoft.com/Start/2014/TaskbarLayout"
    Version="1">
  <LayoutOptions StartTileGroupCellWidth="6" />
  <DefaultLayoutOverride>
    <StartLayoutCollection>
      <defaultlayout:StartLayout GroupCellWidth="6" />
    </StartLayoutCollection>
  </DefaultLayoutOverride>
  <CustomTaskbarLayoutCollection PinListPlacement="Replace">
    <defaultlayout:TaskbarLayout>
      <taskbar:TaskbarPinList>
        <taskbar:DesktopApp DesktopApplicationLinkPath="#leaveempty"/>
      </taskbar:TaskbarPinList>
    </defaultlayout:TaskbarLayout>
  </CustomTaskbarLayoutCollection>
</LayoutModificationTemplate>

LayoutModification.xml for Windows 10 21H1

<LayoutModificationTemplate xmlns:defaultlayout="http://schemas.microsoft.com/Start/2014/FullDefaultLayout" xmlns:start="http://schemas.microsoft.com/Start/2014/StartLayout" Version="1" xmlns="http://schemas.microsoft.com/Start/2014/LayoutModification">
  <LayoutOptions StartTileGroupCellWidth="6" />
  <DefaultLayoutOverride>
    <StartLayoutCollection>
      <defaultlayout:StartLayout GroupCellWidth="6" />
    </StartLayoutCollection>
  </DefaultLayoutOverride>
</LayoutModificationTemplate>

Note that in this version of Windows the LayoutModification does not affect the taskbar as it did previously.