I attach three patches for lisp/textmodes/text-mode.el arising from the
discussion in bug#34671.

The first enables lexical-binding and makes some minor simplifications.

The second makes text-mode no longer reset indent-line-function to
indent-relative locally, a change (info "(elisp) Example Major Modes")
has been promising for many moons.  AFAICT, text-mode works even when
indent-line-function is not set to indent-relative (as I'd hope).  I've
had a quick look through all the modes derived from text-mode in
emacs.git and nothing strikes me as an obvious incompatibility with the
proposed change.  Are there any significant reasons to keep the current
setting of indent-line-function in text-mode?

The third obsoletes the variable text-mode-variant, which is unused in
both emacs.git and elpa.git, and has been recommending derived-mode-p as
a better alternative in its docstring for almost two decades.

WDYT?

Thanks,

-- 
Basil