I am not convinced this is a bug. I've had the same issue with an LG ultrawide (2560x1080) ever since kernel +4.5.7. Linux Mint 18 (4.4 kernel) the monitor worked at its native resolution out of the box. LM19 (think it was a 4.15 kernel) max is 1920x1080 unless you manually set the resolution with xrandr. Did some testing and the last kernel to 'work' was 4.5.7.
I think the problem lies in the EDID implementation by LG. read-edid | parse-edid will list all the modes. 2560x1080 is mode 0, 1920x1020 is mode 11. The "PreferredMode" output by read-edid is mode 11. That I think is the problem. I have no idea how the "PreferredMode" is determined from the EDID.
I am not convinced this is a bug. I've had the same issue with an LG ultrawide (2560x1080) ever since kernel +4.5.7. Linux Mint 18 (4.4 kernel) the monitor worked at its native resolution out of the box. LM19 (think it was a 4.15 kernel) max is 1920x1080 unless you manually set the resolution with xrandr. Did some testing and the last kernel to 'work' was 4.5.7.
I think the problem lies in the EDID implementation by LG. read-edid | parse-edid will list all the modes. 2560x1080 is mode 0, 1920x1020 is mode 11. The "PreferredMode" output by read-edid is mode 11. That I think is the problem. I have no idea how the "PreferredMode" is determined from the EDID.