Kalli I've sometimes used a fine tipped sharpie or equivalent pen to dim leds that are too bright. If you have a fine soldering iron you could also try to just unsolder them. But the safest is the sharpie or tape.

Kalli The radius is much too large to fit a barrel. Can't measure it for you, but it might fit a narrow stock or thereabouts.

Kalli Try the command LoRa.setPins(18, 14, 26); before you do LoRa.begin(868E6); This sets the correct pins, so the LoRa module respons to the begin command, and should work.

Kalli You can set the frequency when you initiate the chip in your program. Read the list of commands for the LoRa library, you'll see it. That frequency should be within what this particular chip can you, you won't have a lot of success setting the 868 chip to 433 for example, but 865 should be fine.