I have been using Nvidia cards with Linux for some time now and was happy with Nvidia providing legacy drivers so I could run modern kernels on my old PC even with an elderly Geforce 210. That’s why I bought Nvidia again :-)
I’m using two fanless Geforce 710 cards on my new PC in a mutliseat configuration because I wanted a silent low power solution for two workplaces on one PC.
I run two independent X Servers on OpenSuSE Leap 15.2 with Nvidia driver 450.57, using KDE 5 Plasma environment. Getting kdm to run two independent logins was a bit tricky (I had to manually edit kdmrc) while the X setup worked quit well with a little help from nvidia-settings :-)
Card 1 drives two adjacent Full HD monitors with slim frames which are rotated 90 resp 270 degrees so a 2160x1920 display results (with a slim line in the middle, of course), using both HDMI and DVI output of the card.
Card 2 drives a smaller monitor for the second workplace.
One USB mouse and one USB keyboard are assigned to each seat.
I also use multiple HDMI sound outputs so both users may listen to different sound sources using headphones.
I’m happy with the setup and how elegantly Nvidia handles even the rotated dual head output to seat 1 with a single metamodes entry in xorg.conf.
By the way: has anybody succeeded in running two independent seats on one graphic card using e.g. DVI and HDMI output for separate monitors ?