You're not the only one - I've been dealing with this for years. For a while it was only between 2 devices so didn't really have a thought of where the blame lay. Now we have used 2 separate NUCs, on 2 separate TVs, have many more consoles... the problem is LibreELEC. I've even run a run of the mill linux distro many times on the same NUCs with no issues at all.
Finally looking into this, as the TV is a pain to change the volume around. Hence finding this.
No amount of amixer/pactl seem to help (about the only thing I can do is mute/unmute right now). Would love to see alsamixer right now.