Assigning USB hub to specific seat in multiseat configuration

On my debian-based machine, I have a working multiseat configuration.

One annoying detail that so far I couldn't fix is that any USB hardware I connect is always assigned to the primary seat.

Scouring the internet, it seems that the solution to this problem is to attach a USB hub to the machine and assign the "ownership" of it to the secondary seat. This way, any device attached to the hub will be controlled to the secondary seat. However, I'm a bit confused about how to assign the ownership.

lsusb allowed me to track the bus position of the hub:

Bus 002 Device 004: ID 1a40:0201 Terminus Technology Inc. Hub

I will be most grateful if somebody will guide me from here...

PS: Initially I thought I had to tweak the xorg.conf settings, but reading the conf.xorg documentation I couldn't find anything relevant. In some other post I also read about using udev, but again... I failed to find a clear how-to on how to achieve this.

This Gentoo article might apply : Multiseat.

Configuration examples in this HOWTO are provided in great detail for a two-seat configuration, with seats labeled "left" and "right", but it is claimed to be easy to generalize to more seats.

The udev section especially describes how to assign the "left" and "right" tags to USB input devices via the file etc/udev/rules.d/99-seats.rules, as well as the KDE desktop manager configuration via the file /usr/share/config/kdm/kdmrc.

I hope that this applies to your configuration.