Microsoft officially supports .NET 4.8 on Server 2016, but note: (it comes with 4.6.2). The installer upgrades, not replaces, existing frameworks. All my legacy apps targeting 2.0, 3.5, and 4.x continued to work without modification.
Reboot the server to clear installation locks, then retry. .net framework 4.8 offline installer for windows server 2016
Windows Server 2016 (version 1607, build 14393) was released with .NET Framework 4.6.2 pre-installed. Over time, many third-party software vendors—especially in fields like healthcare, banking, and manufacturing—have updated their solutions to demand .NET Framework 4.8. Furthermore, Microsoft itself now requires 4.8 for many of its latest server roles, versions of SQL Server Management Studio (SSMS), Exchange Server cumulative updates, and PowerShell 7+. Microsoft officially supports
ndp48-x86-x64-allos-enu.exe /q /norestart Exchange Server cumulative updates