Sure they do. How else would they get from A to B?

Why wouldn’t it? Lots of languages do. In C++ you have __LINE__.

Our sprint at work has been going on for almost 900 days.

External enclosure connected via usb-c. It’s cheap and effective.

Just change your laptop res to 1920x1080, to get the screen DPIs closer. Fun fact: you don’t have to run displays at the highest resolution.

(you said your laptop is 3840x1080, but I assume you meant 3840x2160)

Depends on your budget. Since you’re asking here instead of talking to vendors, I guess you want used, so just browse ebay. You can get something used like this https://www.ebay.com/itm/404093943584

I’ve configured something like this in FVWM2 a long time ago. It was neat for a few hours, but I don’t really see the benefit over regular virtual workspaces.

in i3 I already switch workspaces with mouse wheel on the status bar, which is super easy and seems easier panning around with a mouse.

You would need a locked down device and be physically present at the viewing. Otherwise they can just take a photo of the photo with their phone and share that.