Unsupported official themes are bundled with your friendica installation package, but marked with an empty file (named “unsupported”).
If anyone wants to use unsupported themes, just add this line to your .htconfig.php and the themes becomes visible in the admin panel:
$a->config['system']['show_unsupported_themes'] = true;
… but, we have good reasons for marking these themes “unsupported”
Not longer supported user-themes … maybe usable, maybe not.