As mentioned in the "Steps attempted to resolve the problem" XML::LibXML won't 'just install' in Linux or Unix without the libxml2 packages pre-installed.

This was clear, but why are you concerned ?

:) You don't release XML::LibXML or Alien::LibXML , so its not really any of your business :)

As mentioned in the "Steps attempted to resolve the problem" Alien::LibXML won't 'just install' in Linux or Unix without the libxml2 packages pre-installed.

I kind of doubt that :)

If Alien::LibXML doesn't install libxml2, report a bug, but I think it does install libxml2, just look at https://metacpan.org/source/TOBYINK/Alien-LibXML-0.003/Build.PL

Also, like the docs say, XML::LibXML currently makes no use of Alien::LibXML, so report a bug in XML::LibXML?

Yeah, looks like even if you install Alien::LibXML XML::LibXML won't know anything about it ... standard way you as a user can let it know is through Makefile.PL args INC=/LIB=

Most modules on CPAN do not have a corresponding Alien:: library, and its been that way for most of the history of CPAN ... that a user has to  apt-get install.. before he can cpan SomeModule is kind of a FAQ

So, as maintainer of Spreadsheet::XLSX::Reader::LibXML, there is nothing for you to do, maybe improve your docs to explain the appropriate apt-get steps ...

You could at an utils/installlibxml2.pl to help you out your users, but this stuff doesn't belong in your Makefile.PL, each cpan author takes care of his own distribution

I almost forgot, you could always fork XML::LibXML to use Alien::LibXML and release that on cpan, and submit a feature request ... see upload a fork (unauthorized version),

Hopefully that is clear :)