Had the same problem on fedora (no issue on bazzite, nobara, or arch). First time it was xwayland that kept crashing without a display present for some reason, second time I never solved since I was distro hopping the fedora family of distros but it seemed to be a problem with SDDM
this post was submitted on 02 Jul 2025
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Seems like you were right. I checked my logs with the monitor turned off and the last logged message is SDDM segfaulting.
That seems strange. What's in the log?
I'll check them tomorrow. Should I look for some specific messages? Or the general KDE init process?
Boot log/kernel/dmesg, X/Wayland/kde primarily. Been a long time since I've had to troubleshoot something like this so I don't know the new kids on the block. Maybe upstart or dracut? Whatever manages the boot process now
I checked the logs and can't find anything interesting. I am not that knowlagable so you'll have to forgive me. I used journalctl -b -k to get the log from the current boot and piped it into grep for searching. There is no mention of kde, x11, xorg or wayland.
Ok, editing this while typing. SDDM is segfaulting. I have no idea what that is, but another comment mentioned it. The message reads sddm-greeter-qt(1387): segfault ar 1b .... libLayerShellQtInterface.so.6.4.1... Guess that's the issue?
Yeah that might be it. Sddm is a display manager, you might be using it for your login screen.
You might be able to work around it by just setting the service to restart automatically, so that it comes up properly once a display is attached. But if you can, I would try reproducing it on a fresh and fully updated install, and open a bug report to the maintainers if you can. Linux developers generally try to make really sure their programs don't crash like that.
Might as well try. I have a spare SSD lying around. Tnx for the assistance!
It still starts the KDE session, but it's probably on another term output. Hit ALT+F1 and see if it shows, but it depends on the distro, so it could F1, F6, F7...etc
F1 is just a blank conosle with a blinking curses and you can't type anything into it. F2/3/4 open a new terminal from where I can log in, but none seem to have a KDE session running. Gotta check out the other F keys. Just in case none of the work, is there a solution you know of?
I'm guessing it's similar to this: https://discuss.kde.org/t/plasma-doesnt-start-when-external-monitors-are-plugged-in/17350
You're probably on a laptop and have multiple GPUs enabled at the same time. If not, you're defining Nvidia drivers with something trying to be smart about when to enable the actual outputs or not.
You can either make sure to have the display turned on, or make it super clear to the drivers to always enable a display regardless of whether it detects a display.
I should have provided more details about my setup, but I was kinda hoping that it turns out to be trivial. I am on a desktop PC, AMD gpu, Mesa drivers, one 1440p monitor. Nothing special about the setup. I'll have a look at the URL you provided and try a few things tomorrow.