I’m sitting in a dimly-lit room using my Librem, screen brightness cranked all the way down, and the piercing white wifi/power LEDs in my peripheral vision are very annoying. 
Is there any way to control the brightness of these, either by a hardware hack or software?
I am not opposed to opening up my laptop if necessary, or learning more about the drivers behind these things… 
I don’t think this is possible at all.
In Cryptonomicon, the main character uses a program called xled to turn the capslock light into a morsecode indicator. The package is sadly only fictional.
If you must absolutely work in the dark, I guess you could use some piece of thin masking tape to diffuse the light, or put a small object (such as a pencil eraser) onto those LEDs to temporarily block the light. In your case I doubt it would make sense for you to hack away at the coreboot source code when you can use simple workarounds like that.
Eventually, also try out the “night light” feature in GNOME 3.24 (when it becomes available in PureOS updates eventually), which may allow you to use the screen at higher brightness levels at night without feeling like you’re getting blinded by the blue light spectrum… which will in turn have the side-effect of making the status LEDs perceptually unnoticeable.
I think the EC is the one controlling the LEDs, and they can be dimmed (evidenced by the slowly throbbing led when you suspend), but I have no idea why or even if it’s hardcoded in the EC and not controllable by software.
I would do as @jeff said and just use masking tape on it, or adjust your eye’s light sensitivity in your brain’s control panel.
I’ve got the same problem on a Librem Purism 13 version 3. The white LEDs are just toooooo bright.
Electrical tape. The best solution to most problems.
If you do hack coreboot and figure a way to dim them, please share. Maybe it could be included as an official option someday …
on that. would love to hear more about which EC is responsible for it or how to talk to it at all… Does anyone have pointers on specifics? I couldn’t find anything in the documentation, last I checked.
Lol, you can buy plastic ND filter sheets cheap on ebay or your favorite place You’d have to cut them yourself though and it may leave rough edges and thus be ugly. (a sharp scalpel could work)
I’m a lot more interested in the EC interface and if the source code could be made available, someone could add a dimming feature. I don’t know how the hardware power switching works so if it has a filte ror can’t switch very fast, the PWM could burn it out or be very flickery. A schematic would be great but they aren’t open source.