Manjaro KDE Plasma can't detect my second monitor

[Zesko]

Try to do the solution for RX 560.

Cant boot with HDMI only VGA

Try to add amdgpu.dc=0 in the file /etc/default/grub If you are using KDE kate: kate /etc/default/grub or sudo nano /etc/default/grub GRUB_CMDLINE_LINUX_DEFAULT adds amdgpu.dc=0 then save. sudo update-grub then reboot and connect with HDMI.