With Drupal being the IDP using some SimpleSAMLphp code, and Nextcloud
as an SP, using whatever SAML implementation they added?
The following providers are supported and tested at the moment:
SAML 2.0
Authentication via Environment Variable
> After entering the account details, the account page is shown in
> stead of returning to the Nextcloud instance.
What "the account page"? From Drupal?
> In the Drupal watchdog, I have noted the following:
>
> *Notice*: Undefined variable: attributes in
> *sspmod_drupalauth_Auth_Source_External->getUser()* (regel *289* van
> */var/simplesamlphp/modules/drupalauth/lib/Auth/Source/External.php*).
>
> Could this be related? If not, what am I missing?
Note that the drupalauth module https://github.com/Sanchiz/drupalauth
for SimpleSAMLphp is not distributed (or supported) by the
SimpleSAMLphp project. Still people on this list might be able to
help, of course.
Did you perform the required setup in config/authsources.php mentioned
in the https://github.com/Sanchiz/drupalauth/blob/master/README.md as
well as in the comments near the beginnig of this file?
https://github.com/Sanchiz/drupalauth/blob/master/lib/Auth/Source/External.php