On December 13, 2022, .NET Core 3.1 will reach end of support. From then, Microsoft will no longer provide updates or technical support for .NET Core 3.1. So, it is recommended to move to .NET 6 as soon as possible, or to .NET 7 if you are still using .NET Core 3.1 after the end of support date.
After the end-of-support date, .NET Core 3.1 apps will continue to run as before. But, the security issues in .NET 6 that are fixed after the end of support date will remain a potential security vulnerability for .NET Core 3.1 apps.
Here you can learn more .NET release and end-of-support dates:
PS: Some breaking changes might affect you if you’re migrating an app to .NET 6. You can check more details here: