@robi I'm sorry to disappoint you, but the HTML files I created are very simple. The fancy stuff happens on the uptime kuma page. If you are still interested, here's the code:
<!DOCTYPE html>
<html>
<head>
<title>HTTP 503 - Service unavailable</title>
</head>
<body>
<center>
<h1>HTTP 503 - Service unavailable</h1>
<p><b>Ooops, sorry. The service you requested is not loading at the moment.<br>
Hopefully it's just a restart as part of regular maintenance, so</b></p>
<h2>please try again in a few minutes.</h2>
<p><b>If you keep getting this error message, please visit our <a href="https://status.42bit.io">status page</a>, which usually has more details about longer outages.</b></p>
<p>If you think the 42bit.io / blueplanet.social admin should have a look at this, please reach out to <a href="mailto:admin@42bit.io">admin@42bit.io</p></a>
</center>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<title>HTTP 404 - Not found</title>
<meta http-equiv="refresh" content="15; url='https://42bit.io'" />
</head>
<body>
<center>
<h1>HTTP 404 - Not found</h1>
<p><b>Sorry, I cannot find what you were looking for.</b></p>
<p><b>All I can do is redirect you to my <a href="https://42bit.io">home page</a>, which I will try in a few seconds.</b></p>
<p>If you think the 42bit.io / blueplanet.social admin should have a look at this error, please reach out to <a href="mailto:admin@42bit.io">admin@42bit.io</p></a>
</center>
</body>
</html>