@yaxu @simon It's all detailed in Simon's TIL here:
https://til.simonwillison.net/mastodon/custom-domain-mastodon

Changes to my crusty old Apache server: 3 `ProxyPass` stanzas like:

```
# Mastodon proxy to feed.mccormick.cx
SSLProxyEngine On
<Location "/.well-known/webfinger">
ProxyPass "https://feed.mccormick.cx/.well-known/webfinger"
</Location>
```

And also for `host-meta` and `nodeinfo`. And one `RedirectMatch`:

```
RedirectMatch "/@(.*)$" "https://feed.mccormick.cx/@$1"
```

Also updated [Mastodon conf](https://masto.host/mastodon-usernames-different-from-the-domain-used-for-installation/).