For future reference, some related posts:
Add support for 2.5K and 4K displays with native portrait orientation by installing deb packages with fixed kernel for Jetson Nano: VR display for jetson nano - #5 by Lissanro
The topic where this bug was discussed and a fix was suggested (the unofficial kernel packages mentioned above include the fix): 1440x2560 HDMI display not working - #6 by WayneWWW