The po plugin systematically overrides the title of the homepage with the wikiname. This prevents explicitly changing it with a meta directive. It should rather check whether it was overridden before setting it back.

Here is a simple patch for that:

    diff --git a/Plugin/po.pm b/Plugin/po.pm
    index 6395ebd..a048c6a 100644
    --- a/Plugin/po.pm
    +++ b/Plugin/po.pm
    @@ -333,7 +333,7 @@ sub pagetemplate (@) {
                && $masterpage eq "index") {
                    $template->param('parentlinks' => []);
            }
    -       if (ishomepage($page) && $template->query(name => "title")) {
    +       if (ishomepage($page) && $template->query(name => "title") && !$template->query(name => "title_overridden")) {
                    $template->param(title => $config{wikiname});
            }
     }

Thanks.