Interesting… Are you saying that Windows Server 2025 appears as an update available within Windows Update on Windows Server 2019, or do you just mean that Windows Server 2025 GA/RTM is now available to the public and so you want to in-place upgrade your Windows Server 2019 to it?

Either way, you can indeed successfully in-place upgrade Windows Server 2019, or Windows Server 2022, to Windows Server 2025 (OS Build 26100). Just note that when you perform the in-place upgrade, Microsoft will forcefully/automatically remove all of the Essentials bits from your server and so you will need to run the WSEE Installer on it again in order to reinstall them. However, when you attempt to run the WSEE Installer it will inform you that an instance of WSEE is already installed on the server and it will refuse to run. To get around that issue, I’ve created a small program called the “WSEE Zapper” that will remove the orphaned instance of WSEE from your server thereby allowing you to be able to run the WSEE Installer again. You can download the latest release of the WSEE Zapper program from here.

After running the WSEE Zapper, you can then go ahead and run the WSEE Installer and it will reinstall all of the Essentials bits for you. All of your existing users, devices, backups, settings, etc. will remain in tact during the in-place upgrade and reinstall of WSEE.

As for you needing to purchase a (new) license for Windows Server 2025… I imagine that will indeed be the case. Although, you can always use KMS_VL_ALL, as described under the “Suggestions, Limitations, and Known Issues” section of the main WSEE Installer article, in order to get around that if you so desire.