Native, docker, something else? How starved are you at the moment?

2p2? P2P?

As far as I understood from some research is that I would need to install and run an DHCP server on my laptop, which they did not recommend.

Or simply set up the Pi with a static IP.

there does not seem to be a standard for connecting to a device directly over a single cable and login with a user account.

There is. A cable. You just need two non-identical IPs from the same subnet, e.g. 10.0.0.1 and 10.0.0.2 or whichever you want from the private ranges.

But you’re right, it’s overkill.

I wouldn’t say that. Sure, it’s not the preferred way of restarting a system, but it is a good backup to have if nothing else works. Remotely messing up the network connections for example.

I simply cannot see how using a non-locally running and basically contained AI would work with the secrecy requirements in the (wider) engineering fields. There would certainly be situations where it could help, e.g. the mentioned translation work. Sure, you’d still need an actual human to check what the AI produced, but I can see time savings in those areas.

Many programs used in those fields already use algorithms, rule and filter sets in the daily workflow, so maybe that could be further improved. But overall? No, very unlikely to work.

How are those disks/the box connected to the NUC?

Audiobooks

Do yourself a favor and have a look at Audiobookshelf.

I installed Calibre proper and created the database. But its not aware of my chosen book location.

Calibre uses its own storage/file/folder layout. The usual way would be to set up a Calibre database, point it to the storage location you want, then import your books from wherever they’re stored. Then point Calibre web view towards that library.

Which codecs do you have in your library? Also which resolution/bitrate?

Also, have a look at Kodi as a client.

Where does it fail?

I run a Bookstack instance which works quite well for me.