I was recently sent a link to a video in a series "Ordnance Department - Supply Activities in the AEF [1918]"
(https://catalog.archives.gov/id/24992)
The attached was highlighted. It appears to be a Renault FP (formerly FB) with a GPF gun mounted in the center of the chassis.
I'm not sure what this represents. As a means of transporting a GPF it seems inefficient since the gun has to be mated with the carriage before it can go into action. Firing the gun from the carriage would seem rather limited since it is limited in elevation. Perhaps the FP is a factory hack used for transporting GPF guns around a factory yard.