The preferred way to control a laser using Duet/RepRapFirmware is to use S parameters in G1
This is said by David Crocker, the developer of RepRepFirmware.
I have a Duet controller running RRF3 in my newly built machine. I have everything working, and G1 Sxxx burns when I give manual commands in the console. However the Marlin profile (there is no RRF profile yet) does use M commands and G commands without S parameters. Is there a profile that puts out the G1 Sxxx commands like I need? I hear Grbl-M3 does that, but that one does not allow for many other Gcode commands like homing.