Limit mouse / pen tablet to a single app (i.e. Krita)

Multi seating use case (Using Kubuntu 22.04.1 / Plasma5) with single display: - Huge 65/4K Desktop Screen with plenty of space - Second mouse/Tablet/Keyboard USB input devices plugged on the same computer (and X session) - Second seat / user that wants to use an application with his own input devices, without interfering with the first user (me) using other apps on other areas of the same desktop. What's the best way to achieve this ? The dream would be to be able to "ignore" input events from those secondary input devices for the whole desktop, and be able to set a Window or Application rule to give those input devices to only one (or more) application. I'm using KDE with has per application possible ruleset, but nothing about input / mice / keyboards. An option might be to unregister the input device from XOrg, start a VM (with KVM/Qemu or Virtualbox), and attach the needed devices (USB) to the VM. This is a bit too bad to require a full VM for this, but might be a viable option. If it's possible, would you have a howto ? Do you see another option ?