How to install Linux compatible apropos When I try to get information about apropos, I get the following:
$ which apropos
/usr/bin/apropos

$ apropos --version
apropos from man-1.6g

I tried apropos -r '^report but I get an error:
$ apropos -r '^report'
apropos: -r: unknown option

The man page about apropos is very simple:
apropos(1)                                                                                       apropos(1)



NAME
       apropos - search the whatis database for strings

SYNOPSIS
       apropos keyword ...

DESCRIPTION
       apropos  searches  a set of database files containing short descriptions of system commands for key-
       words and displays the result on the standard output.
...

The above command works on Ubuntu/Linux.
I am not sure if it is because of the macOS apropos BSD?
Is there any way I can install Linux compatible apropos?
On Ubuntu/Multipass, I get the following. The man page has all options:
ubuntu@shin-instance:~$ which apropos
/usr/bin/apropos
ubuntu@shin-instance:~$ apropos --version
apropos 2.9.1
$ man apropos
APROPOS(1)                                       Manual pager utils                                       APROPOS(1)

NAME
       apropos - search the manual page names and descriptions

SYNOPSIS
       apropos [-dalv?V] [-e|-w|-r] [-s list] [-m system[,...]] [-M path] [-L locale] [-C file] keyword ...

DESCRIPTION
       Each  manual  page  has  a  short description available within it.  apropos searches the descriptions for in‐
       stances of keyword.
...
OPTIONS
       -d, --debug
              Print debugging information.

       -v, --verbose
              Print verbose warning messages.

       -r, --regex
              Interpret each keyword as a regular expression.  This is the default behaviour.  Each keyword will  be
              matched  against  the page names and the descriptions independently.  It can match any part of either.
              The match is not limited to word boundaries.

       -w, --wildcard
...
No, it does not have to do with macOS having a &quot;BSD apropos&quot; and Linux having a &quot;Linux apropos&quot;.
Apropos on Linux and macOS is actually the exact same program. The difference you're seeing here is that macOS comes with a rather old version of apropros. You would find the exact same program in Linux distributions from that time period (at that time it was actually a rather simple shell script).
The &quot;-r&quot; option for regular expression was introduced with man-db version 2.5.4 from 2009, of which apropros is part.
You can install a newer version of man-db (and apropos) by having HomeBrew install, and running:
brew install man-db