Connect remote content such as pocket or calibre server to fulltextsearch (via elasticsearch)

Hallo there,
as fulltextsearch only runs with Elasticsearch as search service provider, according to

I’m wondering if I can integrate remote content from e.g. pocket or my calibre database.
According to the dummy tutorial Elasticsearch for Dummies all sources are just node of any kind of content what would be part of the nextcloud cluster.

So Is there any chance to make Elasticsearch speak with pocket via its API?

How about a calibre DB. Besides the default calibre Content server there are also some web servers (Calibre-Web, BicBucStriim, COPS : Calibre OPDS, calibre2opds ) what can access the calibre DB. Here at least, there would some guidance on how to access the DB.

What I’ve learned so far that you need some Integrations plugin in order to speak with remote nodes otherwise you have create it by yourself and adapt to the remote content structure, isn’t it?

I ask as I have many articles and books etc. stored in pocket and calibre and I would like to access them via the reader app but you can doubt if this remains active and last activity was some months ago.
There might something new coming up: Finally an epub library you can read in your browser