How to configure a multiseat setup

mmm. as far as i understand it physically requires one graphics card for each monitor so that would be 4 graphics cards. this is not a limitation in nvidia’s drivers but a limitation in x11. not sure about wayland. there is no way to get around this limitation in x11 because x11 is not under active development anymore. you might get more information asking elsewhere like on the freedesktop.org gitlab since they are actively involved in developing wayland, or maybe on reddit. the only way to do multiseat with a single graphics card could be to use wayland and then going from there

you might also want to look at this: Driver problem with multiseat on one graphic card - #3 by gert.vanhaerents