https://bugs.freedesktop.org/show_bug.cgi?id=109499
--- Comment #4 from Nadal Gonzalo García Zavala snorkellingcactus@gmail.com --- I'm not sure, but is possible the issue were fixed between revisions 43 and 45 of ubuntu kernel 4.15.
Before upgrading the kernel, we reached a solution: - Using EDID emulators, getting xrandr showing both DisplayPort outputting 4k - Dumping the EDID to a file - Quitting emulators, conecting DisplayPorts normally with EDID firmware forced to previously generated file.
Will attach our working EDID file.