So what monitor do you use then?

A 24" 4k Dell monitor. Not perfect, because it has a moire pattern on white backgrounds because of the anti reflection coating.

So this part is pure trigonometry: how much further does a monitor like this have to sit on your desk, to have the same pixels-per-steradian as a 4k 27"?

Yeah. That's what I mean. Just a little further away, same pixel density. It's nice.

On the other hand, brightness decreases 1/distance^2. You would need a brighter panel to achieve the same brightness at a farther distance.

Ah interesting, thanks! On which "virtual resolution" do you set it? Or simply at 2X?

2x, anything else is too blurry.

That monitor has not been for sale for some time, I looked it up. IMHO you are lucky to have one.