Testing tearing - and trying to fix it - on my graphics card I noticed, that nvidia-driver for linux ignores __GL_SYNC_TO_VBLANK=0 for the desktop enviroment / shell. It registers __GL_SHOW_GRAPHICS_OSD=1 and show indicators on every part of the shell, but the vblank is there indicated as active. I am currently trying to test my suspicion, that vsync on plasmashell causes stutters on videoplayback if you open another window (think videoprojection and preparing assets during the screening; or gl render with OBS and stutters in the video). Now, I am tryning this on KDE, but Gnome has also vsync always on, even if there is the enviroment variable declared very low level (/etc/enviroment or desktop enviroment startup script).
I did test my laptop with RTX2060 and desktop with GTX1660. Both KDE and Gnome.