Yes, you can. You will need one of the following:
A virtual camera software that connects directly with your DSLR camera.
A HDMI capture device that can connect to the DSLR HDMI on one side and the desktop USB from the other side.
Some recommended apps that can directly capture DSLR video are SparkoCam (works with both Nikon and Canon DSLRs) and Ecamm Live:
https://sparkosoft.com/sparkocam (Windows)
https://www.ecamm.com/mac/ecammlive/ (Mac)
A recommend capture device is the Magewell HDMI.
After installing SparkoCam/Ecamm, or after connecting the capture device installing the required drivers, you may need to restart your browser.
Then, you can simply select the new capture device in Loola:
