I really like the Grider Elixir course on Udemy and there’s a reasonably easy (if not best practices) way around this if you’ve got OTP27 on your machine.
You can change your deps to refer directly to the local copy of EGD, and then change the one line that calls zlib:crc32:
In mix.exs, change {:egd, github: "erlang/egd"} to {:egd, path: "deps/egd"}.
In your project directory (probably identicon), run a mix deps.compile.
Then find deps/egd/src/dgd_png.erl and change Crc = zlib:crc32(Z,Bin), to Crc = erlang:crc32(Bin).
I’ll see about getting a PR opened against EGD when I can figure out how to get the test suite to run properly.
