Variable: text-mode-variant
text-mode-variant is a variable defined in text-mode.el.gz.
This variable is obsolete since 27.1; don't set it, and instead of
testing its value use derived-mode-p.
Value
nil
Documentation
Non-nil if this buffer's major mode is a variant of Text mode.
Probably introduced at or before Emacs version 27.1.
Source Code
;; Defined in /usr/src/emacs/lisp/textmodes/text-mode.el.gz
(defvar text-mode-variant nil
"Non-nil if this buffer's major mode is a variant of Text mode.")