Hi Boris,
Seems like the change you made to the auth system some time ago broke the Nextcloud app for Collabora.
if I try to open a document in Nextcloud, it gives me an error - unauthorized wopi host
i think the problem is that Nextcloud can’t authenticate through the auth platform. I don’t think there even was an auch for Collabora before you switched to authelia…
Maybe you could add an exception for the nextcloud app so it doesn’t have to authenticate?