I think this is depending on how your running Joomla on Windows (and which version of Windows/IIS or Apche) the http service can access the files as it has system rights.
You should be able the set the access rights needed using the apache access files - there are others here who know more about that… could be you have to refrase your question (setting rights with apache) to get the correct answer.
I’ve given this another thought & the apache access files are probably not the first place to be looking for this. I haven’t set up Joomla on openSUSE before, so I have no specific knowledge there to share.
One thing that could be amiss is the fact that openSUSE stores the httpdocs in a different location, instead of /var/www/… it places them in /srv/www/… (due to different security perspective).