The offline installer is a self-contained deployment bundle. It contains the full payload of the .NET Framework 4.8.1 binaries.
Use the /q (quiet) and /norestart flags: framework 4.8.1 offline installer
Windows 11 originally shipped with 4.8. Attempting to install 4.8.1 on Windows 11 using the offline installer will generally succeed but may trigger a Windows Update conflict if the OS has not been patched to support the newer runtime. The offline installer essentially upgrades the "in-box" feature on-demand. The offline installer is a self-contained deployment bundle