Most new RFCs are authored in an XML format that gets rendered to the officially-submitted plaintext (well, since 2016 (RFC 7990) if you use v3 of the XML schema, that may be submitted directly as the canonical version, otherwise the rendered plaintext is the canonical version.)

So the authors wrote this XML https://www.ietf.org/archive/id/draft-peabody-dispatch-new-u...

That XML got turned in to this plaintext https://www.ietf.org/archive/id/draft-peabody-dispatch-new-u... by the xml2rfc tool https://xml2rfc.tools.ietf.org/

And then that plaintext got turned in to the linked HTML by the datatracker.ietf.org server software, which can be found in SVN https://svn.ietf.org/svn/tools/ietfdb/

At the moment anyway, that XML link won't render per an XML parsing error. For anyone who wants a quick look at what these XML docs look like here's one for UUID6 [0].

[0] https://github.com/uuid6/uuid6-ietf-draft/blob/master/draft-...

The reason it's showing that is because the document says

    <?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?>

But rfc2629.xslt isn't uploaded in the same directory (and Firefox gets real unhappy when it tries to parse the HTML 404 page as an XSLT file). Which is fine, the XML file isn't there to show it rendered, it's to download the source. So you can still just save it.

Not sure exactly what you mean by “look like this”, but several tools for generating RFCs in the standard text format are here: https://tools.ietf.org/

Maybe just wrap your text into <pre> tags? :)