Hello,
This sounds like the same issue I was having.
Most likely is an issue with the latest version of ddcutils.
Have a look here: Computer freezing on loading screen after logging in on Plasma KDE - #8 by pjbcr
One way to fix it is when you get to the login screen do not put your password. Instead press ctrl +alt + F3 and that will take you to a console.
From there you can login as your user and downgrade the ddcutils or restore from a backup.
In some cases if you plug in an external monitor you will also get an working screen.