MacBook (2015) disable boot sound

Question

Before saying that this is a duplicate (or triplicate) I want to let you know that I have tried all the following suggestions:

First I tried these terminal suggestions:

How to Disable the Boot Sound (or “Startup Chime”) on a Mac

Then this with the login scripts

https://jacksadvice.com/turn-off-the-mac-startup-sound/1515/

And a different version 'set volume with output muted'

How To Turn Off The Mac Startup Sound

None of them works!

The only thing that works for me is to mute the sound before shutting down. Now I ALWAYS forget that, so I would not mind a solution that mutes my mac every time I shut it down - and then I'll have to disable mute after boot every time (that I would not mind).

Bonus info

• macOS Mojave
• MacBook Pro (Retina, 15-inch, Mid 2015)

Answer 1

Thanks to @Tetsujin I found this solution https://github.com/matteoacrossi/nobootsound - which works for me, finally.

Answer 2

If you have a headphone port, plug in some headphones. They don't even need to be actual headphones - just the plug with the cable cut off from a broken cable will do fine. When anything is plugged into the headphone port, then Mac will attempt to push the audio boot noise through that instead of the standard speakers.