KDE login theme cannot be loaded. Please help I'm a Linux noob and just want my login screen to be pretty.

At a quick glance, the Sweet Ambar Blue SDDM theme has two versions -- one for Plasma 5 and another one for Plasma 6. You probably want the one for Plasma 6. You can check which version of Plasma you're running in System Settings -> About this System -> KDE Plasma Version.

Be extremely careful when installing Plasma/SDDM themes. They are user-submitted, not always reviewed, and can contain arbitrary code. There have been incidents involving ~~malicious~~ damaging code downloaded through Plasma global themes.

Thank you so much for the help. This was the fix for me. I had the plasma 5 theme and needed the plasma 6 one. Also the last tip about themes is very appreciated and will be considered. <3
- You can also install wallpaper plugins from the KDE store for your lock screen background. I'm a fan of City Grow.
There have been incidents involving malicious code downloaded through Plasma global themes.

No malicious code was involved, just buggy code.
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I'm running Fedora 40 with kde plasma DE if it helps any

As the message is saying, you should try installing QtQuickControls

I have indeed tried that but it hasn't worked.
- Maybe the theme is just broken? Perhaps it’s abandoned and old? I don’t know, I’m just guessing.

You are on Plasma 6 and seemingly all SDDM themes are currently broken.

Use the default theme and try to find ones that work.

Have you tried sudo dnf upgrade QtQuick.Controls Then Reboot If that doesn't work sudo dnf reinstall QtQuick.Controls Reboot again Still no worky Try moving the theme file out of the share folder and reassigning the directory to the new location Then reboot Post any error messages received in terminal

Are you sure QtQuick.Controls is a package?
Looks like an internal QT component to me.

When I upgraded to Plasma 6, I needed to select default theme, upgrade, then re choose my theme. Also upgraded from command line rather than a terminal window.

Have you tried reinstalling sddm and/or the theme? Had the same kind of error a few weeks ago were reinstalling did the trick for me

I've tried switching lock screen themes and gotten it to work temporarily but it goes back to default with that red error text on a reboot.

I've had some VERY similar issues with SDDM ever since I switched to Fedora 40 Sway. Only my issue is with Qtgraphicaleffects, while quickcontrols seems to load properly. I have the following package: qt5-qtquickcontrols2 installed with dnf and it works. Hope it works for you too. But for me, I'm still having Qtgraphicaleffects issues, to the point I ended up rewriting my sddm theme without Qtgraphicaleffects. It's crazy, I know, but it's hard enough to find a decent theme without KDE dependencies as it is (I'm not using KDE Plasma). Finding one without qtgraphicaleffects as well would be even harder.

Just a suggestion...if you've enabled disk encryption during installation, consider enabling autologin for SDDM so you're not having to enter two credentials at boot. You'll rarely ever see your greeter again, so it won't really matter which theme is used.

And if you did not enable disk encryption, consider doing so as the security and privacy benefits are significant for most users.

i do have encryption enabled as security was one of the main reasons i moved to linux. however im going to keep autologin disabled as i like requiring a password after waking from sleep.
- No worries, the screen should always lock after sleep or idle regardless of SDDM. KDE uses a separate kscreenlocker app for that functionality once your desktop session has started. It's worth noting the kscreenlocker doesn't rely on the SDDM theme in any way, as the two are completely separate processes. So, your lock screen will always match your active KDE theme.

Shoo, it’s been a rough week for sddm over here…

Moral of the story. Don’t run Fedora 🥶