Can’t log in after changing SDDM

[Gl0b]

After changing the SDDM theme I can’t log in. I think it’s because the new SDDM forces the first letter in the username to be capital or it might just be an purely visual thing

[andreas85]

Increase your chances of solving your issue:

[HowTo] Increase your chances of solving your issue

Difficulty: ★☆☆☆☆ Strong of its many members, the Manjaro support forum can provide you help whenever you have an issue with your Manjaro installation. But in order to work efficiently, we shall also ask you to commit to a few things. Keep calm and read First some basics: whenever you need to troubleshoot, chances are the solution is already under your nose. Find error messages Very often when an applications crashes, and sometimes when it misbehaves, it prints an error message somewhere. …

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[HowTo] Provide System Information

Welcome to Manjaro! To allow all of us helpful people on this forum TO HELP YOU, we need some basic information about your system. This probably means you described the symptoms of your problem, but now we need some more information to know where the origin of your issue is exactly. Someone else probably linked you to this tutorial, so if you’re reading this in response to a question, please click the link above this text to bring you to the full and unabridged text of the tutorial…

[Nachlese]

If all you did was to change your sddm theme:
since you cannot revert your changes in the Gui, because you cannot log in
you can switch to a TTY
CTRLALTF2
and change /etc/sddm.conf.d/kde_settings.conf
in the [Theme] section
set the theme back to the original (breeze):
Current=breeze

instead of whatever is there currently, what you set it to

use an editor like nano to do it
sudo nano /etc/sddm.conf.d/kde_settings.conf

then either reboot
or restart the display manager
systemctl restart sddm

Having a console filemanager installed
one that will work in TTY as well as in terminal
will help with the process of working at the command line

install mc
pamac install mc

You can use it to do the edit
when started via sudo
sudo mc
but be careful when operating it as root!

Also, perhaps the easiest way:
if you can access your installation from the outside
(boot from the installation live usb, for example - which you might even be using right now to write this …)
then you can use that to make the change,
this time from the fully working graphical environment of the live usb …