After latest update as of Oct 3, 2023, my second monitor was undetected with latest kernel (6.2.0-33-generic). If I boot with previous kernel, it can be detected. After searching a little bit, one suggestion is to delete kscreenrc directory in .local/share and then reboot.
Voila!... it was detected and the second monitor was running well
TQ for the tip.
Source: https://forum.endeavouros.com/t/2nd-monitor-disabled-in-kde-plasma/34239
