The Official UWP ProgressBar Control:https://learn.microsoft.com/zh-cn/windows/apps/design/controls/progress-controls
How can I change it?
I could reproduce your problem. So there are two progress bars: the default one (dotted) is native uwp and the other one(the one you would like to get) comes with the Winui2 nuget package.
How to install and add the nuget:
<Application.Resources>
<XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
</Application.Resources>
xmlns:muxc="using:Microsoft.UI.Xaml.Controls"
<muxc:ProgressBar Width="150" IsIndeterminate="True"/>