Missing option "environment-variable" in configuration page

Steps to reproduce

1. Try to configure SSO with environment variable
2. Option is missing from configuration page : only SAML is proposed

Expected behaviour

An option should exist to switch from SAML type to "environment-variable" type.

Actual behaviour

No option available

Server configuration

Operating system: Debian 9

Web server: Apache 2.4 behind nginx proxy

Database: Mariadb 10.1

PHP version: 7.0

Nextcloud version: (see Nextcloud admin page) 14.0.3

Where did you install Nextcloud from:

List of activated apps:

Enabled:
  - accessibility: 1.0.1
  - activity: 2.7.0
  - admin_audit: 1.4.0
  - announcementcenter: 3.3.1
  - bruteforcesettings: 1.2.0
  - circles: 0.15.2
  - cloud_federation_api: 0.0.1
  - comments: 1.4.0
  - dav: 1.6.0
  - external: 3.1.0
  - federatedfilesharing: 1.4.0
  - federation: 1.4.0
  - files: 1.9.0
  - files_external: 1.5.0
  - files_pdfviewer: 1.3.2
  - files_sharing: 1.6.2
  - files_texteditor: 2.6.0
  - files_trashbin: 1.4.1
  - files_versions: 1.7.1
  - files_videoplayer: 1.3.0
  - firstrunwizard: 2.3.0
  - gallery: 18.1.0
  - groupfolders: 1.3.3
  - impersonate: 1.1.0
  - logreader: 2.0.0
  - lookup_server_connector: 1.2.0
  - metadata: 0.8.0
  - nextcloud_announcements: 1.3.0
  - notes: 2.5.0
  - notifications: 2.2.1
  - oauth2: 1.2.1
  - password_policy: 1.4.0
  - provisioning_api: 1.4.0
  - richdocuments: 3.0.5
  - serverinfo: 1.4.0
  - sharebymail: 1.4.0
  - support: 1.0.0
  - survey_client: 1.2.0
  - systemtags: 1.4.0
  - theming: 1.5.0
  - twofactor_backupcodes: 1.3.1
  - updatenotification: 1.4.1
  - user_external: 0.4
  - user_ldap: 1.4.0
  - user_saml: 2.0.0
  - workflowengine: 1.4.0

Nextcloud configuration:

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder

or

Insert your config.php content here
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)

Client configuration

Browser: Firefox

Operating system: Ubuntu

Logs

Nextcloud log (data/owncloud.log)

Insert your Nextcloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...

The solution I found was to set the configuration option by issuing a sql statement :

update oc_appconfig set configvalue='environment-variable' where appid='user_saml' and configkey='type';

Search the user_saml configuration page implementation for the existing SAML-only type selector and trace how its selected value is saved. Add the environment-variable choice alongside SAML, then verify that it appears in the page and persists as the selected type without requiring the reported SQL workaround.