There are many other lightweight text markup languages with their own processing systems. Those listed here are supported by a toolchain that produces either a plaintext or an RFCXML Internet-Draft.
Most of these toolchains are not widely used and in some cases rely on tools that are unmaintained.
AsciiDoc is a text document format similar to Markdown.
lyx2rfc is unmaintained and was last updated in 2014.
The popular open source editor Emacs includes Nroff mode.
nroff Edit is a Java based WYSIWYG editor for writing and editing Internet-Drafts in nroff. The nroff based Internet-Draft file is edited in the left window while the resulting compiled text version is instantly shown in the right Window as a result of any edit changes.
Nroff Edit is unmaintained and was last updated in 2015.
nroff2xml is a Python script that converts a file in nroff format into v2 RFCXML.
nroff2xml is unmaintained and was last updated in 2013.
Org is a highly flexible structured plaintext file format that is used mainly in the Emacs editor in Org Mode.
Org Mode RFC XML Exporter is an Emacs plugin that exports Org Mode files to RFCXML.