Do you mean using Navidrome as the source of music files for your Raspberry Pis with MPD?
There's an alternative music server called Mopidy, which has a few extensions that would cover this:
- Mopidy-MPD: exposes Mopidy as an MPD server so you can use existing MPD clients with it
- Mopidy-Subidy: allows using music on a Subsonic-compatible server in your Mopidy library.
It's been a while since I used this set-up though. From what I remember it's a bit limited in terms of searching the library.