I somehow stumbled my way into reading about FM DXing — DX of broadcast FM stations.
In doing so, I came across https://servers.fmdx.org/ with a bit over 500 remote FM tuners.
There’s an open-source tuner design: https://github.com/FMDX-org/tef668x-headless-usb-tuner — which looks to have also inspired some commercial variants: https://fmdx.org/projects/guide/receivers.php
And then on the webserver side for them, there’s fm-dx-webserver. Also has a variety of plugins.
The RDSExpert plugin got me curious about exactly what’s in RDS, which led me to this RDS Basics PDF, published by 2wcom (but with a 2006 copyright — not sure how much the protocol has changed since then).