curl itself isn't a requirement to use Joomla or any of the internal HTTP connectors; one of curl, socket (the fsockopen function), or stream connections are used if available.

You've got a mix of items here it seems. The installer should probably add a check if any external connectors are available for use. As for your "failed to download" issue, it is most likely not related to curl missing (if your server was able to fetch the update data then it has a connector).

You are right.. the file downloads correctly, problem is in the return code.
I debugged my issue and the actual problem is in administrator/components/com_joomlaupdate/models/default.php function downloadPackage

                // Download the package
                $result = $http->get($url);

                if (!$result || ($result->code != 200 && $result->code != 310))
                {
                        return false;
                }

in my case $http->get($url); returns $result->code=302 which then returns FALSE, so Joomla "thinks" the update failed, which is not the case.

IIRC there's already an open issue on that (or it's been patched, hard to remember anymore with 400+ open items).

Just for completion, this is the fixed issue #11845
ok then, thanks and sorry for the confusion

@mijalis please try: #11845