Pause the job, preferably with router making a move not a cut, turn the router off manually. Turn your monitor off but not the PC or the controller. Take your break.
When you come back, turn the monitor on, the router on, then hit Pause again to get it to continue what it was cutting.
Or you can stop the job at a convenient move. Take note of where in the G-code it was. Move the bit to 0,0,0. Shut down the controller, the software, the PC as usual.
When you come back, boot up as usual, load LinuxCNC. Home the bit. Move (G0X0Y0Z0) it back to 0,0,0 and it should be right where you left it. Touch off at the original 0,0,0 point otherwise.
Load your file, and scroll down in the g-code to the line you were at when your stopped before. Use the spindle toggle in the software to start the router, then right click on that line # and select "Start from here" or something like that.
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