Back in October at an event in New York City, Microsoft announced that its Your Phone app will get the ability to mirror your Android phone's screen. According to a report from MSPoweruser, the feature is just about ready to go, and Insiders will be testing it soon.
You'll need a few things for this. For one thing, you need a PC that supports BTLE Peripheral mode, and you'll also need a phone from the Galaxy S8 or Galaxy S9 series running Android 7.0 or later. According to the report, more devices will be added in the coming weeks.
It seems likely that the first to try out the new feature will be Windows Insiders on the Skip Ahead subset of the Fast ring. Fast ring app updates are locked down as Microsoft prepares for the RTM of Windows 10 version 1903, so they probably won't get it until 19H2 previews start showing up.
At this time, Your Phone only allows you to send and receive text messages from an Android phone, and it lets you view and interact with the last couple dozen images from your phone's gallery. Third-party applications have already mastered Android mirroring, such as Dell's Mobile Connect app.