Support for Windows 10 Mobile will expires in December. Microsoft has already stopped developing versions of Windows 10 Mobile that add new features to its mobile operating system from 2017.
But as of December, all updates stop, marking the end of the company's mobile operating system. 
Microsoft recently updated the Windows 10 Mobile support page to add this change. After 10 December, any Windows 10 Mobile on build 1709 will stop receiving updates, whether it's secure or not. The company will also stop free support options or online technical assistance.
Users in build 1703 will see the end of support even earlier, from 11 June 2019. If you're wondering about builds 1803 and 1809, these builds never reached Windows Phone.
After the end of the support, Windows Phones will continue to work, but some features will end.
Automatic and manual backups for settings and apps will stop after 10 March 2020. And services such as sending photos and resetting devices will be stopped by December of 2020.
The official Microsoft guideline for customers using the platform is to "switch to a supported Android or iOS device" and use Microsoft applications on one of these platforms.
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In a moment, Microsoft will suggest that we leave Windows and computers back and move to other operating systems (eg Linux)