Thinks I hate from #GNU and a bit from #Unix/#X11:

- #Emacs Calc (core package) depending on nonfree (not
GPL compatible) Gnuplot for plots. They should rewrite
the output for GNU #Plotutils and enhance the second
to have 3D plot support.

https://spdx.org/licenses/gnuplot.html

Distributing Gnuplot forks as a patch
against the main one -mandatory- makes Gnuplot's
code unshareable with other projects, period.

- #Texinfo (official GNU documentation format)
depending on #Texlive where tons of stuff in the official
release it's nonfree. Again, that should be a core feature
for #texinfo, and not depend on #tex at all.

https://wiki.parabola.nu/TeXLive_freedom_verification

- #Xedit might look as a crude X11 text editor but it
supports vi command AND it has an embedded Lisp
interpreter (compatible with a bit of CL/core Elisp
code, enough to do Math). It's 2026 and still doesn't
support neither UTF8 nor Unicode fonts. Trying to
enforce them under Xaw3D (LD_PRELOAD) will crash XEdit.
That editor would have lots of support if it supported them.
It's far lighter than Emacs and with the bundled Lisp
you might do wonders.

Back to Groff/Troff.
At least under #Hyperbola GNU (and future #BSD) with #mandoc
and maybe by promoting groff they are pretty much safe
even to typeset formulae into diferent formats, you can
pretty much use Groff for Math paper drafts and then
use TexLive for standard, rigid academic layouts.