TL;DR, noon on a distant planet like Pluto orbiting a sunlike star is about as bright as civil twilight on Earth.

I can’t remember where I heard about “Pluto time” (probably a vsauce video) but the original NASA site with the calculator is archived and no longer works.

The site linked above seems to recreate the original. You input your latitude and longitude and it spits out the next time (evening or morning I presume) that it will be as bright as noon on Pluto.

I did some quick napkin math and determined that the luminous flux on Pluto at noon should be around 100 lux. I checked the outdoor light sensor at the time given on the site above and it’s in the ballpark, around 80 lx. That’s light enough you probably wouldn’t need a flashlight just to get around but probably not enough to read by, maybe.

As for my own conworld, yinrih can see a much broader spectrum than humans, so my napkin math doesn’t apply, but it does give an idea of how other things that require sunlight would fare. You’re probably not doing agriculture without artificial lights, for one thing.

In the Outer Belt they cultivate a type of high-latitude plant with large leaves to absorb as much of the feeble polar summer sunlight as possible. It forms large cysts filled with a creamy liquid that it uses to survive the winter. Selective breeding has allowed it to thrive on the dwarf planets of the Outer Belt, but still with a heavy dose of artificial light provided by orbital infrastructure and terrestrial illumination.