This seems to be quite a lot of trying. Can you please remove all of your installation attempts?
Then it’s probably easiest to switch to Arch Linux 
or just use a toolset manager like asdf-vm. It will be able to install, run and change appropriate version sets as you specify them per project.
Also in the official documentation there is a compatibility matrix that tells you which version of elixir is known to work with which version of Erlang.
Just remember that the runtime version of Erlang needs to be equal to or greater than the version used for compiling.
