Can you post a full inxi? Optimus-Manager? I thought that was an Nvidia thing to switch between gpus? I don’t see an Nvidia graphics card from the inxi snippet that you posted. On my Dell laptop (xfce) I have the laptop Display as disabled and the External display as primary with settings to ignore the lid being closed. I also have a card that uses the i915 driver. So, I would check over the display settings again and figure out if you do have an Nvidia card and do need optimus-manager.