I know that there is no Kodi Plugin for this, but maybe this can be solved on OS level? I'm not this far into Linux to develop this from scratch on my own - I'd need to rely on a pre made solution for this. Am I the first one asking for such feature?
The Linux audio subsystem (alsa) is very flexible, but thereinlies the problem. It's so flexible (and technically dense) that you can almost never Google the article with precicely what you're looking to achieve written clearly; it's what Harry Potter would refer to as "one of the Linux dark arts". So you're not the first person to look for an EQ function but there's no Kodi plugin, nothing native in LE, and no mortal human-readable HOWTO guides that I know of ot deal with it at alsa levels. Yay, we 
alsa!
Is there any ambition/motivation available from libreelec Team to implement such feature? 
There is a reddit thread with a ready made solution, but this stuff needs to be "migrated" to libreelec - also wouldn't wonder, if the used alsa plugins are missing in libreelec. 
€dit:
Well this also is a bit old ...
It should be a Kodi feature we inherit and not something specific to LE, hence there's not much ambition among staff.
