So last night after some soldering I got this thing started:
It was so easy it's almost not allowed. I installed Nerves, nerves_init_gadget, nerves_io_rc522, followed some instructions and it was working just like that. Crazy! You can see here how little code it is: https://gitlab.com/Nicd/duck-tag
I've always been at most a very light hardware tinkerer. I never thought it could be so easy to get Elixir running on my device with sensible defaults, shell access via USB, firmware pushes over USB/network etc. I think the Nerves team has done a really great job and deserves all my gratitude.
Thanks Nerves team!
PS. I see they have a donation page at https://opencollective.com/nerves-project and I'm going to give some on my next payday. You should too.