Every now and then, when I boot up my PC, I get no login screen shown - in fact the monitor behaves as if it is getting no signal from the PC, despite having shown POST messages and grub screen prior to going black when it was supposed to show the login screen.
I can’t find any real pattern to when this happens. I might be able to boot and get the login screen showing normally multiple times over and then suddenly, a few days later, the problem reoccurs…
Now, Debian does boot up OK, because upon having entered my password and hit enter, I do get the Plasma desktop showing up as normal.
As mentioned, I’m on Debian - version 12- and here are some additional version and hardware details:
I have tried to grab the startup logs from the most recent time this happened and will post below.
A few irrelevant things have been removed from the log dump, but it still has a lot of lines, so please let me know if I can get some more concise logs in a different manner?
Posting links is not allowed for new users - you get the ability to do that after being active for a while and proving you are not a drive-by spammer. How great of an idea is this setup for a support forum will be left as an exercise to the reader. I’ve edited your message to have a working link.
Now about your problem - the log shows some errors in the SDDM greeter, with things like:
Nov 07 20:31:09 workstation sddm-greeter[2185]:
Failed to find a Kirigami platform plugin
Nov 07 20:31:09 workstation sddm-greeter[2185]:
file:///usr/share/sddm/themes/breeze/components/
VirtualKeyboard.qml:12:1: Type InputPanel unavailable
...
Nov 07 20:31:09 workstation sddm-greeter[2185]:
QXcbConnection: XCB error: 148 (Unknown), sequence: 196,
resource id: 0, major code: 140 (Unknown), minor code: 20
Your version of Plasma is mighty old - it isn’t even the latest 5.27 (which is 5.27.11) so it is going to be very hard to trouble shoot that. It is very unfortunate that Debian 12 doesn’t even track bug fixes to the “stable versions” of packages they ship.
I would try to check if you have installed a third-party theme - you can check by looking a the directory /etc/sddm.conf.d/ and see if you have some configuration files there that might have content that looks like this:
[Theme]
Current=maya
(in my case I’m using the custom theme “maya”).
If so - you can try to reset to the default theme by removing the line that starts with Current= and restart your PC, see if that solves it.
Otherwise, I’d try to maybe use a different login manager (maybe LightDM or GDM) and seriously think about switching to a Linux distribution that cares more about Plasma users.
I was sort of fearing that it could be an unresolved bug in what proves to be an outdated version of Plasma.
Is there any reliable way to run a more recent version on my current system, or will that require installing a different distro, from scratch?
If the latter is the case I might just live with this silly error until we get the next major release of Debian, which shouldn’t be much more than ~8 months away, by now
That being said, I’m still curious to hear what distro you would suggest if I want to stay as close to the Debian experience as possible, while also staying away from Ubuntu (and Snaps in particular)?
By the way, I did check to see if I had the /etc/sddm.conf.d directory on my system, but this is not the case, and I think then I’m probably on the default/vanilla Plasma theme, with some UI tweaks here and there.
I will look into switching Login manager although this is unknown territory to me.
Switching to a new login manager should be as easy as installing another login manager and choosing to switch to it in the configuration dialog that you get during installation. If you already have another login manager installed, you can invoke the configuration dialog by running sudo dpkg --reconfigure PKGNAME
I can recommend trying gdm first.
Regarding alternative non-Ubuntu Debian-based alternatives - I’m not familiar with any: the Debian-deriviatives scene is packed with Ubuntu-variants. There may be others, though I’m familiar with none. You may want to try a snap-hating Ubuntu derivative like Linux Mint - the latest version is based on Ubuntu 24.04, so you’d still be on Plasma 5 - but at least it will be the latest most up to date and supported 5.27.11. me personally, I don’t understand the snap hate - if you don’t want to use snap packages, don’t install any.
The other popular option is to run Debian testing - with all that entails.
I’ve now switched from sddm to lightdm (steered away from gdm because of all the dependencies).
Just for kicks, I checked if I was able to login to the wayland session, but that was as broken as it has always been (black screen with frozen prompt), so now my fingers are crossed that at least I will consistently get the login screen displayed
On the subject of snaps, I wouldn’t say that I hate them, but got a little sick of being forced to install the snap version of certain apps such as Firefox (at least this was the case, last time I used Ubuntu) and honestly I just prefer good ol’ deb packages, or the odd flatpak if need be.
