dism /online /set-edition:<serverstandard or serverdatacenter> /productkey:<...> /accepteula

Windows Server 2025 Standard	TVRH6-WHNXV-R9WG3-9XRFY-MY832
Windows Server 2025 Datacenter	D764K-2NDRG-47T6Q-P8T8W-YP6DF
Windows Server 2025 Datacenter: Azure Edition	XGN3F-F394H-FD2MY-PP6FD-8MCRC