Black electrical tape works wonders. I have applied it copiously. With some care on many devices it can be applied invisibly, and it can be removed if you need the led.

Outdoors, I've made all my lights activated by motion and door-opening sensors, and have been transitioning to light with less splash. E.g. 592nm LED strip placed 2ft over the ground pointed downwards along walkways, so they only light up the walk way and just provide enough light to see clearly and safely... instead of floods.

I find it so much nicer to not have my night vision blown out by my own lights.