https://www.cnbc.com/2019/01/18/microsoft-ending-windows-10-mobile-says-switch-to-iphone-or-android.html

Microsoft says anyone who still uses its Windows 10 mobile platform — once called Windows Phone — should switch over to an iPhone or an Android phone. A change to the Windows 10 Mobile support page was first spotted by Thurrott, a site that covers Microsoft.

Microsoft said that on December 10, 2019 it will stop sending "new security updates, non-security hotfixes, free assisted support options, or technical content updates from Microsoft for free." In other words, there aren't going to be any more updates, and only a few phone models will even be supported until that final date.