Support for Windows 10 Mobile will end in December. Microsoft has already stopped developing versions of Windows 10 Mobile that add new features to its mobile operating system since 2017.
But starting this coming December, all updates will stop, thus marking the end of the company's mobile operating system. 
Microsoft recently updated its Windows 10 Mobile support page to include this change. After December 10, any Windows 10 Mobile on build 1709 will stop receiving updates, regardless of security or not. The company will also stop providing free support options or online technical assistance.
Users on build 1703 will see the end of support even earlier, starting June 11, 2019. If you're wondering about builds 1803 and 1809, those builds never made it to Windows Phone.
After end of support, Windows Phones will continue to function, but some features will be discontinued.
Automatic and manual backups for settings and apps will stop after March 10, 2020. And services like photo upload and device reset will stop starting in December 2020.
Microsoft's official guidance for its customers using the platform is to "switch to a supported Android or iOS device" and use Microsoft apps on one of those platforms.
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