Hi @syclonix, thanks for your suggestion…much appreciated! It may be of interest to you to read another forum thread on this topic @ https://developer.tobii.com/community/forums/topic/ultrawide-monitors/
Wherein a number of other users have proposed successful workarounds that may be relevant for your situation, so I would encourage you to check it out and let us know what you think. As you will see, most of the implementations are based similarly to your second suggestion of a free-standing mount.
In any event, as you pointed out, this kind of setup is still not officially supported so we cannot recommend it, but if you do indeed manage to setup your eye tracking device well with your monitor, feel free to pass along the details!
Also, you are correct that if the monitor height is adjusted then (Assuming the eye tracker is not mounted to the screen) you would need to readjust the free-standing mount also accordingly.