No need to apologize !
Even though the link and code you shared used alpine, it was still very educative. I was able to analyze the code and create a component that does exactly what I want. Its also quite pretty, so I am very proud. This code uses only Phoniex LV vanilla, no extra CSS no extra anything !

core_components:

  @doc """
  Renders a progress bar for an ongoing operation.

  ## Examples

      <.progress_bar hidden=false progress=15 />
      <.progress_bar hidden=false progress=20 message="Activating system ..." />
      <.progress_bar hidden=false class="cool-bar" />
  """
  attr :hidden, :boolean, default: true, doc: "whether or not to show the progress bar"
  attr :progress, :integer, default: 0, doc: "the current progress of the bar"
  attr :message, :string, default: "Operation in progress ...", doc: "the message to show while the bar is progressing"
  attr :class, :string, default: nil

  def progress_bar(assigns) do

    assigns = assign(assigns, :circumference, 2 * 22 / 7 * 120)
    assigns = assign(assigns, :offset, assigns.circumference - assigns.progress / 100 * assigns.circumference)

    ~H"""
    <div class={@class} hidden={@hidden}>
      <div class="flex items-center justify-center">
        <p class="text-lg font-semibold"><%= @message %></p>
      </div>

      <div class="flex items-center justify-center">
        <svg class="transform -rotate-90 w-72 h-72">
            <circle cx="145" cy="145" r="120" stroke-width="30" fill="transparent" class="stroke-gray-700" />

            <circle cx="145" cy="145" r="120" stroke-width="30" fill="transparent"
                stroke-dasharray={@circumference}
                stroke-dashoffset={@offset}
                class="stroke-indigo-500" />
        </svg>
        <span class="absolute text-5xl stroke-black"><%= @progress %></span>
      </div>

    </div>
    """
  end

Usage in my_app_live.heex.html:

<div class="min-h-full max-w-full mx-auto py-6 sm:px-6 lg:px-8">
  <.progress_bar hidden={false} progress={40} message="Activating system ..." />
</div>

Will produce the following:

Screenshot 2023-09-06 1441401387×524 14.1 KB

Possible improvements

Currently i am not sure if there is a more elixir way of updating the assigns:

assigns = assign(assigns, :circumference, 2 * 22 / 7 * 120)
assigns = assign(assigns, :offset, assigns.circumference - assigns.progress / 100 * assigns.circumference)

But other than that, I am pretty happy with it.

Additional info

For those of you curious, you can also check this other solution someone else provided in SO:

I hope this helps!