Last week, Microsoft issued a statement on the support of Azure AD Connect version 1.x. It reaches end of support on August 31st, 2022. That is exactly one year from now.
What 'unsupported' means
In-place upgrade of Windows Server on an Azure AD Connect server is not supported. While you might pull it off, in the long term you might find yourself with an unsupported Azure AD Connect installation with the following consequences:
Functionality may break
If you run a retired version of Azure AD Connect, it may unexpectedly stop working and you may not have the latest security fixes, performance improvements, troubleshooting and diagnostic tools and service enhancements.
Moreover, if you require support, Microsoft may not be able to provide you with the level of service your organization needs.
AUTOMATIC UPGRADES MAY BE DISABLED
Azure AD Connect does not support Automatic Upgrades in unsupported conditions.
Previously, this measure was applied to Azure AD Connect installations running on Windows Server 2008 and Windows Server 2008 R2 and to Azure AD Connect installations running older versions of the .NET Framework. Now, you might find that your Azure AD Connect v1.x installation no longer automatically upgrades.
For many admins, Azure AD Connect is a 'fire and forget' type of installation. With Automatic Upgrades unavailable, you might see organizations stuck with troubled Azure AD Connect versions.
UPGRADES MaY BREAK
Automatic Upgrades may not be a problem. To go to newer Azure AD Connect versions, you can still perform manual upgrades. However, these manual upgrades may break at any point, too.
Call to Action
Please upgrade your current Azure AD Connect v1.x installation to Azure AD Connect v2.x before August 31st, 2022.
Performing a swing migration for Azure AD Connect is the preferred way to get to Azure AD Connect v2 when you're currently running Azure AD Connect version 1.x on Windows Server 2012 and/or Windows Server 2012 R2.