Remove headline from title page in Quarto beamer presentation for Szeged theme

Question

How can I remove the headline in a Quarto beamer presentation when using the Szeged theme?

I tried various approaches to remove the headline, such as creating a special frame option (which unfortunately removed the headline also for the following two slides). As far as I know in Quarto I cannot create a new environment around a frame as suggested in this post and \setbeamertemplate{headline}{} does not do anything when it's declared inside \defbeamertemplate*{title page}.

---
title: "My Presentation"
format: 
  beamer:
    theme: Szeged
    include-in-header:
      text: |
        \defbeamertemplate*{title page}{customized}[1][]
        {
          \setbeamertemplate{headline}{}
          \def\beamer@entrycode{\vspace*{-\headheight}}
          \usebeamerfont{title}\inserttitle\par
        }
editor: visual
---

# Quarto

Some text.

Answer 1

If you ditch the automatically added title page, you can add one yourself and e.g. select a plain frame which does not have a headline:

---
format: 
  beamer:
    theme: Szeged
    include-in-header:
      text: |
        \defbeamertemplate*{title page}{customized}[1][]
        {
          \setbeamertemplate{headline}{}
          \def\beamer@entrycode{\vspace*{-\headheight}}
          \usebeamerfont{title}\inserttitle\par
        }
editor: visual
header-includes:
- \AtBeginDocument{\title{My Presentation}\begin{frame}[plain]\titlepage\end{frame}}
---

# Quarto

Some text.