The OS support isn't quite as ironclad as that. Windows Server 2019 was the last version where .NET Framework 3.5 will be supported for the lifetime of the OS; while later versions still include 3.5 as an optional feature, it's only going to be supported until January 2029 (when 2019 goes out of support), even if the OS is still in support.
We know .NET Framework 4.x will still have to be supported through October 2034 to meet similar support obligations for Windows Server 2025; but Microsoft could easily let that be the end date for 4.x if they wanted, even if Windows as a whole is still supported.
We know .NET Framework 4.x will still have to be supported through October 2034 to meet similar support obligations for Windows Server 2025; but Microsoft could easily let that be the end date for 4.x if they wanted, even if Windows as a whole is still supported.