CedricB wrote

As far as I understand Web Authentication doesn't allow web redirect in https so basically users not logged in can anyway use internet in https... http becoming obsolete I hope to find a solution.

First of all, any Captive Portal which uses interception works by redirecting HTTP requests, so yes, it is the case with "Vouchers" authorization, too.
And no, clients using HTTPS can not access the Internet without prior authorization. They may have to use a HTTP request to make the portal page appear, but they cannot circumvent authorization. Read on for a solution how to avoid the user to manually request a webpage by HTTP to force the portal page to appear.

Next, HTTP is not becoming "obsolete", what makes you think so? This might be the dream of companies selling SSL certificates, but dreaming is ok.

Every modern mobile device still uses HTTP to see wether it is connected to the Internet or blocked by a Captive Portal at a public hotspot. This technique is known as "Connectivity Tests" or "Network Location Awareness" and it still requires HTTP. Those devices will open the portal page even if the user didn't request a web page at all.

So, HTTP will not become "obsolete", at least not in our lifetime.

CedricB wrote

Do you have any recommandation how to force the portal page to appear whether users request http or https webpage?

That's why the "Connectivity Test" aka "Network location awareness" has been introduced by Google, Apple and Mickeysoft for devices using their OSes. It is even implemented on laptop/PC OSes nowadays.

On older device not supporting CT or NLA you must request a HTTP webpage to force the portal page to appear. Anyway, all traffic (HTTP and also HTTPS) should be blocked as long as the user has not been authorized through the portal.