At start make sure that asdf current erlang is set to 23.x and then use this command: asdf install elixir ref:v1.10.4. It would compile from source, but in Elixir case is not a really big problem since it does not take much time to compile.

v1.10.4 is Elixir git tag attached to specific commit, you can also use branch name like master (which is automaticcally attached to latest commit in specific branch) or even specify any commit reference (for example to check some PR).

I think the issue is here in the mapping of OTP versions and Elixir precompiled builds in the Bob builder: https://github.com/hexpm/bob/blob/acd0d66213066e9b42f318b0da0818c01bb11c34/lib/bob/job/build_elixir.ex#L61

That said I thought I remember an earlier Elixir 1.10.x which was incompatible with OTP-23 and don’t know enough about that to make a simple PR.

@josevalim described it here:

Therefore, Elixir v1.11 will be released in October 2020. If there are any important bug fixes, we will continue releasing patch versions for Elixir v1.10. On that note, the latest Elixir v1.10.3 is already compatible with Erlang/OTP 23.

Source: Elixir v1.11 will be released in October 2020

So we have a problem with missing correct clasule for reference v1.10.4 which means it fallbacks to "v1.10." <> _ which then specifies such otp releases: ["21.3", "22.3"].

@josevalim I would like to suggest using Version.compare/2 which should reduce code. Just for example instead of:

  def elixir_to_otp(ref) do
    case ref do
      "v0" <> _ -> ["17.3"]
      "v1.0.0-" <> _ -> ["17.3"]
      "v1.0.0" -> ["17.3"]
      "v1.0.1" -> ["17.3"]
      "v1.0.2" -> ["17.3"]
      "v1.0.3" -> ["17.3"]
  # …

we could just write code like this one:

  def elixir_to_otp("v" <> version) do
    cond do
      Version.compare(version, "1.0.4") == :lt -> ["17.3"]
  # …