Microsoft has released Windows 10 Insider Build 21376 with a preview of a new default font for Windows 10 called ‘Segoe UI Variable’ Microsoft has switched to Segoe UI Variable for some operating system elements but is still adopting it across all visual elements. Microsoft states that this rollout of the new font will progress over time. Also included with this release are many fixes that increase performance, fix crashes, and further fix issues with their new News & Interests newsfeed app. The new font uses variable font technology to dynamically scale at tiny and large sizes without using its legibility.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-introduces-windows-10s-new-default-user-interface-font/