well, I’m not sure traditional is the right word, multiseat has been used for a very long time. It used to be a bit better supported. The issue is that since the migration to wayland, it has become… a lot less supported. It is still possible, but most of the guides are x11 guides for a reason.
EDIT: I should say I hope seatd at some point could support multiseat but at the current time I don’t think it has any facilities to, systemd-logind / elogind do support multiseat, but I dont currently use them