Date: Wed, 6 Apr 2022 11:20:52 +0200
From: Andreas Röhler <andreas.roehler@easy-emacs.de>

M-x woman RET file RET

errors saying:

Debugger entered--Lisp error: (error "WoMan can only format man pages
  written with the usual ‘-man’ macros") signal(error ("WoMan can only
  format man pages written with the usual ‘-man’ macros"))
  error("WoMan can only format man pages written with the usual `-man'
  macros") woman-decode-region(1 21597) woman-decode-buffer()
  woman-process-buffer()
  woman-really-find-file("/usr/share/man/man1/file.1.gz" t "*WoMan 1
  file*<2>") woman-find-file("/usr/share/man/man1/file.1.gz")

However from bash, manpage appears correctly.
Also would read nicely from:  "man file > file.txt"

woman.el doesn't use the 'man' program.  It is implemented completely
in Emacs Lisp.  So what 'man' does is not really relevant; what _is_
relevant is that Someone(TM) should step up and volunteer to keep
woman.el up-to-date with all the recent advances in roff markup.
Until that happens, the error you see above is intentional, meant to
alert you, the user, to the fact that the man page cannot be reliably
formatted this way.

That workaround attached does it here.