This is the README for the plex package, version 2023-12-17.

This package provides LaTeX, pdfLaTeX, XeLaTeX and LuaLaTeX
support for the IBMPlex families of fonts. Serif, Sans,
Sans-Condensed and Mono families are available in eight
weights: Regular, Light, ExtraLight, Thin, Bold, Text,
Medium and SemiBold (with corresponding italics).

To install this package on a TDS-compliant TeX system
download the file "tex-archive"/install/fonts/plex.tds.zip
where the preferred URL for "tex-archive" is
http://mirrors.ctan.org. Unzip the archive at the root of an
appropriate texmf tree, likely a personal or local tree. If
necessary, update the file-name database (e.g., texhash).
Update the font-map files by enabling the Map file plex.map.

To use, add any of

\usepackage{plex-serif}
\usepackage{plex-sans}
\usepackage{plex-mono}

to the preamble of your document. These will activate
IBMPlexSerif, IBMPlexSans and/or IBMPlexMono as the serif,
sans or mono font, respectively. To activate the Sans font
as the main text font, use

\usepackage[sfdefault]{plex-sans}

LuaLaTeX and xeLaTeX users who might prefer type1 fonts or
who wish to avoid fontspec may use the type1 option. 

Option scale=<number> may be used to scale the fonts.

Option condensed for plex-sans selects the condensed
versions as the default. Commands \plexsans and
\plexsanscondensed allow for local use of the non-default
sans family. Commands \plexsanslgr and \plexseriflgr 
activate the LGR encoding.

Font encodings supported are OT1, T1, TS1, LY1 and LGR.

The following options select lighter bold fonts:

  sb semibold
  mb medium
  tx text

and the following options select lighter regular fonts:

  l  light
  el extralight
  t  thin

For slightly heavier regular fonts use the options

  txmd textmd

The nomap option to plex-mono will suppress the tex-text
mapping of TeX "smart quotes" and other ligatures into
unicode glyphs for xeLaTeX and luaLaTeX.

The OpenType fonts were obtained from

https://github.com/IBM/plex/

and are licensed under the SIL Open Font License, Version
1.1. The text may be found in the doc directory. The type1
versions were created by cfftot1 and re-named in compliance
with the Reserved Font Name provision. The support files
were created using autoinst and are licensed under the terms
of the LaTeX Project Public License. The maintainer of this
package is Bob Tennent at rdtennent(at)gmail(dot)com.