Use Filezilla and SFTP.

Are we talking main + guest network, or 2,4GHz + 5GHz, or something else?

No. This installation is so old it precedes the AIO image. “Standard” docker image, redis, mariadb.

Docker behind a Traefik proxy with crowdsec checking (adds additional lag). Ryzen 2700x 32GB local machine. All storage on SSD.

The web interface is very usable, switching subpages takes maybe half a second max without it being cached by the browser.

Could of course be quicker (as basically everything ever), but as we mostly use it with the Windows sync clients and Android apps we never really have any issues.

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.

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.