Hmm.. It might be something that's specific to the earlier install. I think i upgraded from 15.10 to 16.04 to 16.10. On a different system (Dell T3420) I installed 16.04 and upgraded to 16.10. That system has 2x 4k screens and shows also the lower resolution of 2560x1440.
I'm gonna try a fresh install on the XPS13. Maybe even a 16.04 install and update that one. I'll keep you posted.
Hmm.. It might be something that's specific to the earlier install. I think i upgraded from 15.10 to 16.04 to 16.10. On a different system (Dell T3420) I installed 16.04 and upgraded to 16.10. That system has 2x 4k screens and shows also the lower resolution of 2560x1440.
I'm gonna try a fresh install on the XPS13. Maybe even a 16.04 install and update that one. I'll keep you posted.