I'm a lefty, but for some reason back in the stone age, when I started using a mouse, I felt more comfortable keeping the buttons set for a right-hander. But when it comes to using a trackpad or a trackball mouse, it's much easier configuring it left-handed.

For Synaptics and other trackpads (even those with virtual buttons), it's easy to use Gnome Tweaks to have configure the two separately. But when I use a trackball on my normal desk, I can't separate it from the mouse configuration. Is there a simple way to parse the USB pointer device to look for "trackball" and set things appropriately?

My guess would be to look at using xinput and adding a special configuration for the device in /etc//etc/X11/xorg.conf.d/ somewhere.

That should show how your system sees your input devices and the name of the device and its id number. Use those to make an entry in the xorg.conf.d directory.

(GNOME might get in the way though.)

Edit: see also "man libinput"