The bitfile can still be loaded through the RIO Device Setup Utility.
The driver installation behaves a bit differently if only the LabVIEW RunTime is installed. In order to install the RIO Device Setup Utility:
1. Go to the folder where the installer for the R-series driver
2. Open Products >> NI-RIO_DeviceSetup >> RioDeviceSetup.msi
3. Run this installer (as administrator if possible).
4. Now the RIO Device Setup should appear when you search for it in Windows
5. Proceed with the steps from "Option 1: Download a bitfile using NI RIO Device Setup"
to finish loading the bitfile to the R Series device.