Previously it was talked about that Elixir would create a telemetry library and then Phoenix (and other libraries like Ecto, etc.) would use it.

And the end goal was to have a Phoenix web UI that would come out of the box that you could goto and see a bunch of really useful things about your server's health, the BEAM but more importantly app specific things like DB query times and all of those interesting stats you would want to see. The beauty of it was you would get all of this for free / nearly free in terms of the work you had to do as an app developer.

Did all of that get scratched for OpenTelemetry? Do you happen to know of a timeline when end users could expect to see the benefits of this new standard in Elixir apps?

The official website at https://opentelemetry.io/ doesn't show Elixir as being a supported language.