Current considered solution is Authelia. Alternatively, Nextcloud seems to embed an identity provider starting from NC 14.
: check whether the Nextcloud IDP exists and its capabilities
According to the documentation, it can be deployed either over bare metal (good, since we use LXCs), or over K8s.
The documentation references multiple deployment scenarios:
Open Authentication v2.0 database - Dovecot
Roundcube supports the XOAUTH2 mechanism starting from version 1.5
A maintained plugin exists (https://www.dokuwiki.org/plugin:oauth).
: test the configuration and paste a sample here
An Apache module is available in the Debian repositories, starting from Debian Jessie.
https://packages.debian.org/sid/libapache2-mod-auth-openidc
https://github.com/zmartzone/mod_auth_openidc
: test the configuration and paste a sample here