Test custom Caption in WinUI 3 on Windows 10 21H1 (Unpackaged app with a Manifest) by copying and updating styles from generic.xaml :
<Style x:Key="WindowCaptionButton" TargetType="Button">
<Style TargetType="ContentControl" x:Key="WindowChromeStyle">
(colors, size, CornerRadius to make rounded System Buttons)
and a scrolling text for testing, but not very smooth like with Direct2D...