How do I create a select-element in a liveview-form?

Yep, that’s how it’s done. Select options are a list of tuples in the form of {text, id}. I usually put it in assigns, though if it’s static it doesn’t much matter I don’t think:

category_options = Enum.map(Testing.Categories.list_categories(), &{&1.name, &1.id})

socket =
  socket
  |> assign(:category_options, category_options)

<.input field={@form[:category_id]} type="select" options={@category_options} />