Digest authentication not supported?

Hello all,

I’m experimenting with nextCloud on a Raspberry Pi.

Setup :
Raspberry Pi 3 with Raspbian.
Default apache 2 server configured with SSL and Digest Authentication for the documentRoot
PHP 5.6
nextCloud 12

When trying to test the CalDAV functionality, it systematically fails .
Logs indicate that the authentication is aborted: nextCloud expects Basic Authentication.

Is this intentionally ?
If not, anyone who has some pointers as on how to change the nextCloud Authentication mechanism ?

Regards,

Bert