…just joined here in order to clarify a few things for future reference,
hopefully it will save others from similar headaches as per above.
Erlang Solutions’ instructions per se indeed don’t / won’t work on Mint ‘as is’. But…
that has absolutely nothing to do though whatsoever with Mint somehow having a different package base or dependencies etc.
The ‘fault’ lies in their installer’s routine, erlang-solutions_1.0_all.deb…that’s what’s to be blamed 
What it does, is that it parsers /etc/issue for the identification of the numerous Ubuntu & Debian versions,
then nicely sets the repositories accordingly to the version detected.
But…by parsing the non-standard /etc/issue, which will 99% return a different id,
in any Ubuntu / Debian derivative out there…it fails on such.
A by far more proper way would be if they checked /etc/lsb-release.
Actually, even better than such, if we are to go with the freedesktop standards nowadays, /etc/os-release instead.
Although as we all understand…admittedly even then some distros would fail to comply, lol…
Hopefully Erlang Solutions will revisit their os detection routine at some point,
at least without relying entirely on /etc/issue…
For the time being, on Ubuntu derivatives, someone can ‘bypass’ the erlang-solutions_1.0_all.deb method,
by following these instructions here…
https://forums.linuxmint.com/viewtopic.php?p=1603722#p1603722
That’s for older Mint 18 (xenial). For Mint 19 (bionic), obviously the line should instead be ubuntu bionic contrib…
…bend wasn’t the first one to be hit by this, that’s what i’m trying to say
Just noticed his thread over at LM’s forums today…
where people also told him to use the erlang-solutions.deb,
apparently unaware of what goes on. Had i seen his thread earlier,
i’d have posted / replied there, but maybe that’s for the better…
Thought i’d mention the above here, so in case some other fella in the future,
from whatever other Ubuntu / Debian derivative comes asking,
can probably understand what’s going on & save his/her time…
Or so that you guys around here can guide him on what to do to easily add the repos & packages properly:
all that’s needed is to add the appropriate matching repo in sources.list
Or maybe the ES people eventually notice it, and then fine-tune / somehow tweak the routine in their ‘setup’ .deb… 
