It definitely used to all happen client side, if your graphics stack was messed up, then those tools wouldn't apply those effects. I haven't used those tools i

It definitely used to all happen client side, if your graphics stack was messed up, then those tools wouldn't apply those effects. I haven't used those tools in a couple years, but I doubt it's any different now. I know that Google Meet (the tool I use nowadays) still does it client side. Every now and then I break something when updating my Nvidia drivers on Linux and I can no longer blur my background.