I had a little trouble getting this up and running but now that I have read and re-read I caught a few things maybe possibly update the wiki camera section with making sure "Embed Webcam Stream" and " Do not append extra HTTP qualifier " are un-checked. Those were the two things holding me back. I did update the lighttpd.conf file so you do not have to use the "user:pass" portion of the address. Another note is using the cgi-bin/currentpic.cgi isn't using RTSP, it is using a static image that is updated at whatever frame rate you have set in the Dafang firmware and the duet grabs whichever frame happens to be the most current still image which is currentpic.cgi when it does its update at your specified interval.

I've been looking to do the same, found this on the Endurance Laser website.

How to Connect to Duet3D Wifi Board
The PWM input of the laser is connected to the Fan0 output of the Duet board.
Power control teams
M106 S127 – 50% power
M106 S255 – 100% power
M106 S0 – Laser Off

https://endurancelasers.com/wiring-endurance-lasers-to-top-popular-boards-cnc/

I don't see why it won't work.

I had a little trouble getting this up and running but now that I have read and re-read I caught a few things maybe possibly update the wiki camera section with making sure "Embed Webcam Stream" and " Do not append extra HTTP qualifier " are un-checked. Those were the two things holding me back. I did update the lighttpd.conf file so you do not have to use the "user:pass" portion of the address. Another note is using the cgi-bin/currentpic.cgi isn't using RTSP, it is using a static image that is updated at whatever frame rate you have set in the Dafang firmware and the duet grabs whichever frame happens to be the most current still image which is currentpic.cgi when it does its update at your specified interval.