https://www.techradar.com/news/microsoft-announces-it-will-soon-stop-supporting-apps-for-windows-8

Microsoft has announced that it will cease to support apps for Windows 8 at the end of October.

In a blog post, the company clarified that come October 31, the Microsoft Store will stop accepting apps from developers targeted at Windows 8/8.1 (or indeed Windows Phone 8.x).