Remote debugging elixir on docker container

Hi there,
on my macbook pro (OS Big Sur / Darwin 20.3.0) I am trying to setup the erlang observer on an elixir app running in a local docker container.

On container shell I can successfully run:

iex --name myserver@ --cookie mycookie -S mix phx.server

and even:

iex --name someproc@ --cookie mycookie -e "Node.connect(:'myserver@')" -S mix run --no-start

The nodes can successfully see each other.

The container remaps the EPMD port from 4369 to 43691 and I’d like to launch a local shell like this:

iex --name user@ --cookie mycookie -e "Node.connect(:'myserver@')" -S mix run --no-start

but even if the repl starts, the Node.connect / to myserver@ fails.

The most complete guide I’ve found in order to accomplish this goal is here, but I don’t know if - following that - it is correct to use as REMOTE_HOST and even trying I cannot reach in the new shell the remote process.

Any clues/suggestions?

Thank you