I’m trying to mirror the display from my laptop to an external monitor connected via HDMI, I’ve opened display settings but the checkbox for mirror display is grayed out, so it’s currently working as an extended display.
I’m running an AMD Apu with open source drivers if that helps
https://forum.xfce.org/viewtopic.php?id=13659
looks like a bug in xfce.
You should be able do that using xrandr
xrandr --output HDMI-1 --auto --same-as LVDS-1
dont forget to edit HDMI-1 and LVDS-1 to suit your needs output of xrandr command should let you know what to use
Maybe do a google search before asking 