The Meteor docs used to include a recommendation to use redirect.pizza to redirect an old domain to a new one. This was very helpful recently, as support at my dns host said they were unable to do it for some reason. Checking the old link, I no longer see reference there to this service.
Suggestion: consider adding a reference to this service to the M3 docs.
1) Redirect with clientside Javascript at static HTML page
<head>
<title>This website has been moved</title>
</head>
<body>
<!-- If Javascript is enabled, try to redirect -->
<script type="text/javascript">
window.location.href = "https://yournewcompany.com";
</script>
<!-- If Javascript is not enabled, show link to new website -->
<noscript>
<center>
<br>
<br>
<h1>This website has been moved</h1>
<p>New address is:
<a href="https://yournewcompany.com">https://yournewcompany.com</a>
</p>
</center>
</noscript>
</body>
</html>