I'm late to the party, as usual. Damned timezones. This year I'm going to tackle with a small handful of languages, but primarily Elixir and Gleam. This is my first time trying this languages in earnest, so expect some terrible, inefficient and totally unidiomatic code!
Here's day one:

Elixir

part_one =
  File.read!("input.in")
  |> String.split("\n", trim: true)
  |> Enum.map(fn line ->
    line
    |> String.split()
    |> Enum.map(&String.to_integer/1)
  end)
  |> Enum.reduce({[], []}, fn [first, second], {list1, list2} ->
    {[first | list1], [second | list2]}
  end)
  |> then(fn {list1, list2} ->
    {Enum.sort(list1), Enum.sort(list2)}
  end)
  |> then(fn {list1, list2} ->
    Enum.zip(list1, list2)
    |> Enum.map(fn {x, y} -> abs(x - y) end)
  end)
  |> Enum.sum()

part_two =
  File.read!("input.in")
  |> String.split("\n", trim: true)
  |> Enum.map(fn line ->
    line
    |> String.split()
    |> Enum.map(&String.to_integer/1)
  end)
  |> Enum.reduce({[], []}, fn [first, second], {list1, list2} ->
    {[first | list1], [second | list2]}
  end)
  |> then(fn {list1, list2} ->
    Enum.map(list1, fn line ->
      line * Enum.count(list2, fn x -> x === line end)
    end)
    |> Enum.sum()
  end)

IO.inspect(part_one)
IO.inspect(part_two)