[piskov]

Surely there’s an app for that: “Duet display” exists more than a decade (sidecar basically sherlocked it). Also something called Astra or Luna (don’t remember exactly).

[rovr138]

Hah, same thing I thought!

Went looking on the AppStore and I had bought Duet on December 2004!

They went subscription based, https://www.duetdisplay.com/

[ttepasse]

There are also Apps which display HDMI input streams over USB-C. Orion and such.