I have been told that I can control my Canon 600EX-RT (as well as Canon non-RT hotshoe flashes) as a slave with a Godox (Flashpoint) R2 X1 transmitter/receiver if I have the 600EX-RT attached to a Godox (Flashpoint) R2 Receiver.
I have been seriously considering replacing my Godox (Flashpoint) X-1 Transmitter/receiver with the Godox (Flashpoint) R2 Pro Transmitter because the display on the Pro unit is easier for my old eyes to see than the display on the X-1.
The Godox (Flashpoint) R2 Receiver costs $40 at Adorama while the R2 Pro Transmitter costs $69.
Could I slave the Canon 600EX-RT flash with the R2 Pro Transmitter if the 600EX-RT was mounted on the R2 X1. That way, I could have both the advantages of using my 600EX-RT as a slave and have the newer R2 Pro Transmitter at only a $29 increase in cost over purchasing the R2 Receiver....