Thats from the current nextcloud docs:

We strive to bring Artificial Intelligence features to Nextcloud. This section highlights these features, how they work and where to find them. All of these features are completely optional. If you want to have them on your server, you need install them via separate Nextcloud Apps.

I mostly try to read the docs, but sadly good documentation is pretty rare.

I doubt using secret managers is popular among self hosters. These products are targeted at larger deployments, not homelabs.

You‘re supposed to host this yourself.