Hot reloading to add Logging?

I am trying to understand better the Elixir Logger. I have read Compile time purging of logger levels - #12 by aseigo and Logging from within Remote Session - #6 by ityonemo
I have an app where I did something like:

# runtime.exs
config :logger, :console,
  level: System.get_env("LOG_LEVEL", "info") |> String.to_existing_atom()

but now I am thinking this is not possible like I hoped. I read about the option for :compile_time_purge_matching… so if I have

config :logger,
  backends: [:console],
  compile_time_purge_matching: [
    [level_lower_than: :info]
  ]

in my config.exs but I have log level of :debug in runtime.exs, there are no more debug messages visible because they have been removed during compile.

One problem I noticed on a built release is that when I remote attach to a running app, I still see debug messages even when the level is :info. I think this maybe has something to do because my process in remote iex is different that the process of the running app (?) but this is just my guess – I really don’t understand why.

The other example I wanted to see was how to hot reload a module to include logging statements? If I am remote into running app with all debug statements removed at compile time, how could I add debugging back in so I can debug running production instance?

Thank you for your wisdom. I know this is a complex topic but I am trying to get more infos for how to approach.