[gary@gary-thelio ~]$ systemctl status display-manager
● sddm.service - Simple Desktop Display Manager
There is no sddm.conf.d to require a login password.
Seeking to stop autologin and require password
Go into system settings, look for the SDDM kcm (I can’t remember the exact text) and turn off auto-login.
I pasted your post to perplexity.ai and this is the answer:
Perplexity:
You don’t need to add a password setting to SDDM—you need to disable autologin.
SDDM reads configuration from these locations, in this order, with later settings overriding earlier ones:
/usr/lib/sddm/sddm.conf.d/*.conf
/etc/sddm.conf.d/*.conf
/etc/sddm.conf
So a missing /etc/sddm.conf.d/ does not mean there is no configuration; check /etc/sddm.conf as well.[man.archlinux]
1. Find the autologin settings
Run:
sudo grep -RnsE '^[[:space:]]*(\[Autologin\]|User[[:space:]]*=|Session[[:space:]]*=|Relogin[[:space:]]*=)' \
/etc/sddm.conf /etc/sddm.conf.d /usr/lib/sddm/sddm.conf.d
Messages saying a file or directory does not exist are harmless here. The output should identify the file containing the autologin configuration.
2. Disable it
If /etc/sddm.conf contains something like:
[Autologin]
User=gary
Session=plasma
edit it:
sudoedit /etc/sddm.conf
Change that section to:
[Autologin]
User=
Session=
Relogin=false
An empty User= disables automatic login. Setting only Relogin=false is not enough: that option controls automatic login after logging out, rather than the initial login at startup.[man.archlinux]
If the settings are in a file under /etc/sddm.conf.d/, edit that file instead. If they come only from /usr/lib/sddm/sddm.conf.d/, leave the packaged file untouched and create a local override:
sudo mkdir -p /etc/sddm.conf.d
sudoedit /etc/sddm.conf.d/99-disable-autologin.conf
Put the same three settings under [Autologin] in it. Remember that any conflicting settings in /etc/sddm.conf still take precedence.[man.archlinux][wiki.archlinux]
3. Test
Save your work and reboot to test the login screen. Use your existing Linux account password; you are not creating a separate SDDM password. Don’t restart sddm from your running desktop just to test this, since that will terminate the graphical session.
This is the best example of how stupid AI is, just using system settings is ten times easier , done it a couple of times myself. ( can also be done on the PLM).
I’m surprised you have SDDM installed. I guess you didn’t switch to Plasma Login Manager. No problem, though.
Easiest method is through the GUI method IMHO. You likely have sddm-kcm installed and if you don’t have it, install it and reload the session. After that, you would have a new option in the System Settings that mentions login directly in its name and you could change things there. Unsure the SDDM options are different compared to the Plasma Login options, but yeah.
You could, and in my humble opinion should, switch to Plasma Login Manager if you’re using Plasma. That’s what KDE seems to recommend and support so… yeah. If you want to do that, remove SDDM, install plasma-login-manager and then tell the system to use that as the display manager instead of SDDM with # systemctl enable plasmalogin.service and then you could reboot the machine. I believe by default, the manager doesn’t have autologin.
Since the AI is just a giant scrapper for all of the internet, I’m not surprised it went with the editing config files approach. I don’t think it is “stupid” for taking that path. It is not only something that it more or less natively understands, it is also produces more easy to perform steps than following someone through a GUI that changes more often than a config file for a service.
Although, I will admit that just… putting the guy’s problem into the AI and copy-pasting what it gave you back to him is… I don’t know, it doesn’t sit right with me.
Well it is just that scraping I am annoyed about , making sites unreacheble at time, or have to confirm I am a human being trying to reach a certain site. Something called Anubis popping up, where the other day blocked the site because it was not configured the right way. Going through a captcha (or whatever it is called) with blurry pictures on it, and trying to pick the right ones, we didn’t have that before this aggresive piece of … was around 
sudo pacman -Syu plasma-login-manager
sudo systemctl disable sddm
sudo systemctl enable plasmalogin
reboot