Happens with both 6.4.0 and 6.3.4 msi installers. Message is Error 1303: The Installer has insufficient privileges to access this directory: C:\Program Files\LibreOffice\program.
I have tried adding “Run as Administator” option for msi files as decribed at https://www.lifehacker.com.au/2018/05/how-to-fix-windows-10s-missing-run-as-administrator-option-for-msi-files/ , but get same error, near the end of the installation