After: The underside of the same desk, but with significant changes. A black channel has been mounted to one of the struts. Most of the cable mess is gone, with only short stretches of cables coming out of and going into the channel. The PC has been suspended from the desk, off the floor as well.
https://tooting.ch/system/media_attachments/files/110/388/804/440/514/781/original/c19ba3d319e8be43.jpg