Thanks. The file xrandr.txt indeed shows the HDMI connection is limited to 1920x1080. It also shows that's the "current" mode but it lists no "preferred" mode, which does support the idea that the monitor can do higher resolution...
The manufacturer's specs mention that 4K is limited to 30Hz over HDMI. But that should be fine. It just means the monitor can't do HDMI 2.0. Most likely the monitor only supports HDMI 1.3 or 1.4. I think the main problem here is probably the HDMI cable. If it can only handle HDMI 1.2 or lower then you will not see the 3840×2160 30Hz option. So I suggest getting a newer cable that supports at least HDMI 1.3. Why Windows 10 doesn't have the same issue, I don't know. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to mutter in Ubuntu. https://bugs.launchpad.net/bugs/1890418 Title: External monitor will not display to 4k Status in mutter package in Ubuntu: Incomplete Bug description: I have a Toshiba radius 11 laptop which has a 4 k native screen. I have connected an Asus PB287Q 28" external monitor (https://www.asus.com/us/Commercial-Monitors/PB287Q/specifications/) over HDMI which displays the full 4K resolution when running under windows10 but will only reach a maximum resolution of 1920x1080 under ubuntu 20.04, same hardware just dual booting. Under Monitor Preferences this monitor is detected as an "Ancor Communications inc 28" and the monitor preferences provides a number of resolution steps up to 1920. If I issue "xrandr --addmode HDMI-1 3840x2160" this resolution is added to the monitor preferences pick list but attempting to apply it results in "the selected configuration for displays could not ..." message To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1890418/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
