What you need to know
Some Windows 10 users have reported seeing a full screen warning about next year's end of support date.
Users running Windows 10 in in-eligible PCs are being prompted to learn about how they can transition to Windows 11 by buying a new PC.
The full screen prompt has no button to never show it again.
Microsoft has started showing full screen warnings about the upcoming end of support date on Windows 10 PCs. Users on Reddit have reported seeing the prompt, which began appearing after this week's Patch Tuesday updates were installed, and encourages the user to learn more about how they can transition to Windows 11.

Windows 10's end of support date is currently set for October 14, 2025. After that date, Windows 10 users will no longer receive critical security and bug fix updates, leaving any Windows 10 PC connected to the internet vulnerable to any newly discovered security exploits. 

https://www.windowscentral.com/software-apps/windows-11/microsoft-begins-showing-full-screen-windows-11-ad-on-windows-10-pcs-as-end-of-support-date-looms