stuff like

xset s off
xset -dpms
xset s noblank

and/or there may be other ways in guis to do so too.

can put that in some startup shell bobbins, or wherever its supposed to go in configs. but i tend to just run it in terminal (from fish history) once it bothers me enough to switch it off. … am not on my usual computer just now, so i had to look that up. plucked that from 2nd result of a websearch for “x11 noblank off”.