Logseq can be launched as a desktop app and in a web browser and has both iOS and Android apps. Official sync is a paid feature but there are other options (e.g. Syncthing).

Navidrome with Substreamer on mobile for auto-generated recommendations based on already played music works great for me.

Calibre Web has Kobo integration, although I'll admit I haven't been able to make it work so far: https://github.com/janeczku/calibre-web/wiki/Kobo-Integration

Jitsi also provides integration with Matrix chat.

Applying negative selection, QNAP has a terrible security track record and WD has terrible performance and security track record. So if you want something that's mostly plug and play, Synology it is, consider a "+" model if there's any chance that you may expand beyond the simple file sharing use case.

Disclaimer: I currently own three Synology boxes (718+, 220+, 216j) and a QNAP TS-453D running Proxmox (for fun and as an attempt to move towards a HW vendor-independent solution).