Things I learned today: Multi-Seat setup on Debian.
Because of how Linux user sessions work, I thought there must be a way to hook up two monitors, two sets of keyboard & mice, and split the displays between Intel integrated graphics and my NVidia GPU.
Debian has a guide on it and I was able to set it up so that my son and I could play Minecraft java edition with friends online. Worked like a charm with a standard Debian install (no VM's!)