$ sudo apt install curl git
$ git clone https://github.com/asdf-vm/asdf.git ~/.asdf --branch <version> 
$ echo ". \"$HOME/.asdf/asdf.sh\"" >> ~/.bashrc
$ echo ". \"$HOME/.asdf/completions/asdf.bash\"" >> ~/.bashrc

install erlang and elixir plugins

  # erlang deps (asdf doesn't manage deps)
$ sudo apt-get -y install build-essential autoconf m4 libncurses5-dev libwxgtk3.0-gtk3-dev libwxgtk-webview3.0-gtk3-dev libgl1-mesa-dev libglu1-mesa-dev libpng-dev libssh-dev unixodbc-dev xsltproc fop libxml2-utils libncurses-dev openjdk-11-jdk 

$ asdf plugin add erlang https://github.com/asdf-vm/asdf-erlang.git
$ asdf plugin add elixir https://github.com/asdf-vm/asdf-elixir 
$ asdf install # everything inside .tool-versions 
$ asdf current
elixir          1.14.3-otp-25   /home/ryan/dev/citerun/.tool-versions
erlang          25.3            /home/ryan/dev/citerun/.tool-versions

install pheonix

$ sudo apt-get install inotify-tools # linux only
$ mix local.hex
$ mix archive.install hex phx_new

run

run mix setup to install and setup dependencies
start Phoenix endpoint with mix phx.server or inside IEx with iex -S mix phx.server
visit localhost:4000