lol, I've done this a bit, but it makes everything look broken
A dot of black permanent marker seems to work well. Blocks out enough light to remove the distraction, while still allowing enough to indicate something working.
These, sometimes, look a little better than electrical tape. I haven't used this brand, it was just the first one I found. [1]
I've been sticking these things on everything. Not this particular brand either, but I doubt there's much difference between brands.
It allows enoughlight through so you can see what's going on but not enough that will illuminate the room or distract you just by being there.
I never thought to look for that before! Amazing. I currently have a lot of black electrical tape over everything.
That only helps when the device doesn't have an LED that's inside an open casing and so ends up visibly shining from every hole in the device and/or through the thin plastic itself.
these are the worst, or when they are on a button like my monitor
Black masking tape. It's not opaque enough to block the light entirely; this means you can do a few layers to dim it to taste. Once that's sorted, a quick trim with an x-acto blade will tidy up the edges and make it all look intentional from a distance.
Sometimes I still want to see the LED. In this situation, I use blue painters tape, and keep adding layers until the LED is at a reasonable level. You really need to check this in a completely dark room to get it right.