SUMMARY STEPS TO REPRODUCE 1. launch kde neon 2. connect one or two external monitors 3. go to settings/display configuration OBSERVED RESULT: Only laptop screen shows - no external monitor is displayed, nor primary button signalling several screens are detected - despite the monitor flickering and shortly after reporting no signal then staying dark. EXPECTED RESULT external monitors are displayed and display config can be adjusted from there. not being able to use large screens is really crippling. SOFTWARE/OS VERSIONS Windows: no macOS: no Linux/KDE Plasma: (available in About System) KDE Plasma Version: 5.19.3 KDE Frameworks Version: 5.72.0 Qt Version: 5.14.2 ADDITIONAL INFORMATION: This bug appreared after a reboot after a software update.
Issue with Kscreen not enabling outputs properly when a screen is plugged...while arandr does it just fine. I've also had erratic behaviour with Kscreen and plugging in external screens. This mostly affects screen plugged into the HDMI port on my laptop (a Lenvovo X1 Carbon 6th Gen - I know this laptop had issues witht he HDMI port but this has been corrected and is not the issue in that case - see below). Sometimes it works completely fine and then it stops. Usually it starts working if in addition to the plugging in a screen on the HDMI I also plug in a screen on the display port (suddenly everything comes on). Moreover, sometimes Kscreen detect that the screen is plugged in / unplugged (it says t detect the configuration has changed) but still no new screen appears. But today I had a BREAKTHROUGH :) The screen was not detected but then I looked at xrandr --verbose and saw that xrandr did detect the screen just fine (listing all the right resolutions etc.) So I installed arandr (another GUI for xrandr). There I still could see only my laptop screen, but the going to menu > Outputs the HDMI port was not greyed out and I could tick "enable", then the screen appeared in both arandr and Kscreen. So while in theory Kscreen also has the option to enable an "output" which it calls enabling a "screen", it does not seem to work quite as expected in some cases. It is to note that anyway the screen was not enabled when plugged in and even with arandr it required an extra step to enabling it. Happy to paste some output that might be useful to debug this.
Thank you for the bug report. Unfortunately we were not able to get to it yet. Can we ask you to please check if this is still an issue with Plasma 5.25 or 5.26? If it is, please change the status to CONFIRMED when replying. If not, or if you can't because you no longer use this setup, you can change the status to RESOLVED WORKSFORME. Thanks a lot! --- Gauthier, if screens show up in the KCM but aren't *enabled* properly, your issue is different. oscar6echo's issue is that external screens aren't appearing in the KCM at all. If you're still having this issue with Plasma 5.25 or 5.26, please file a new bug report for it. Thanks to you too!
(In reply to Nate Graham from comment #2) > Thank you for the bug report. Unfortunately we were not able to get to it > yet. Can we ask you to please check if this is still an issue with Plasma > 5.25 or 5.26? > > If it is, please change the status to CONFIRMED when replying. If not, or if > you can't because you no longer use this setup, you can change the status to > RESOLVED WORKSFORME. Thanks a lot! > > --- > > Gauthier, if screens show up in the KCM but aren't *enabled* properly, your > issue is different. oscar6echo's issue is that external screens aren't > appearing in the KCM at all. If you're still having this issue with Plasma > 5.25 or 5.26, please file a new bug report for it. Thanks to you too! Hi Nate, Sorry if I wasn't clear but in my case the screens were also not appearing at all in KCM. This is why trying xrandr was a breakthrough as they did appear there. Then using the arandr gui I could see the screens were not enabled. Once enabled in arandr then they would show up in KCM. So what that meant was that xrandr/arandr was more reliable at *detecting* screens (or kscreen not reliable picking up the info from xrandr). Now, this issue was quite sporadic and not easy to reproduce, and to reply to your question what I can say is that I haven't had it in a while now so I'll mark it as RESOLVED WORKSFORME.