I know this has been open a while but i just figured out that this appears to be linked to your Primary screen resolution. I have a Mac Studio and a Studio Display and it is set to 5k for my photo editing and the Drift Screensaver stopped working like the rest of you experienced on the extended display a long time ago. I needed to adjust the resolution of the Studio display today and set it to Default for display 2560x1440 and low and behold i returned to my desk after leaving it alone for some time and both screens had the Screensaver working. Joy of joy i thought, But not quite!
My second screen is a Ultra-wide with a maximum resolution of 3440x1440 and no matter what setting i have my studio display set at if it is anything over the 1440 it will not display the Screensaver on both displays.
Would be interested to know if this is the same for the rest of you or if you have 2x screens the same and they are set the same and it is still not working. To me this appears like a simple fix related to variable resolutions for the screensaver but nothing these days appears to be a simple fix!