There was something like this a few years ago, "Elixir for Rubyists": https://thoughtbot.com/blog/elixir-for-rubyists
If you like the presentation format rather than written format, I did what was called by one reviewer "a delightfully thorough" intro to Elixir for Rubyists: https://www.youtube.com/watch?v=uPWMBDTPMkQ
https://pragprog.com/titles/sbelixir/from-ruby-to-elixir/
From Ruby to Elixir, by Stephen Bussey. He's also written a book named Real-time Phoenix which I also found pretty helpful.