Users are forbidden from much of the internal Sonos data.

I have /status and /tools.htm bookmarked here, haven't checked access on recent firmware.

I use Subsonic to provide music service locally, but ever since customsd.htm was blocked, it seems I can no longer enable or disable the related services.

The customsd page was disabled in a recent firmware update so that Sonos can drop support for locally implemented music services, they want to switch to cloud-only access for SMAPI.

If you want to use it, you have to use an S1 system.