According to the post in announcements:

High Resolution Audio

With S2, Sonos speakers now have support for high resolution audio, 24-bit, 44.1/48kHz for FLAC/ALAC only. This support is for local music libraries shared from computers and network attached drives. We’ve updated the article on Sonos supported music formats here.

The Sonos Arc is a Dolby Atmos soundbar, and S2 brings support for that audio to Sonos for home theater and music. Dolby Atmos can be read from Dolby Digital Plus, Dolby MAT, and Dolby TrueHD.

Hi-

i know about and understand the current limitation on streaming to 16 bit content vs 24 bit from local files. My question is whether this is a hard constraint or something that may be opened up in the future?  I have much Tidal 24 bit content that I can either play from the Sonos app or via Roon, and it works rock solid on other non-Sonos endpoints.  I’d be happy to deal with slightly longer buffers or whatever were necessary to remove the assymetry of treatment of local/streamed content bit-depth. 
 

thanks. 

Tidal HiFi is regular 16/44.1 FLAC. Tidal 24bit is, as far as I can make out, MQA encoded. The industry appears to be split down the middle on whether MQA is a good thing or an unwanted, lossy, DRM scheme. I would not be holding my breath awaiting Sonos support for it.

Well, I don’t think that’s true - there’s lots of Tidal content that is not MQA. but even for the MQA content, the Tidal app can present the content to non-MQA DACs (e.g. those connected directly to a computer via USB) in whatever format the DAC can consume. If i have a Schiit / other DAC that doesn’t have MQA, it presents the stream as Redbook 16/44 if the DAC can take that, or 24/48 if it can consume that. 
 

However, that’s not my use case - I’m streaming via Roon, which can do the MQA unfold or not similarly depending on the capability of the endpoint. 
 

but I’m not even talking about MQA content - there’s lots of non-MQA 24-bit FLAC content, that Roon is down-bit-depthing from 24 to 16 before presenting it to the Sonos.  Note I’m not even talking about sample rate. Happy to post pictures of my bitstream if that’s helpful. 

Ah, I see. It’s the intermediate transfer format between Roon and Sonos which concerns you, rather than direct streaming from online service to Sonos player. 

Since Roon appear to tweak the interface at their end -- https://help.roonlabs.com/portal/en/kb/articles/sonos says “As new devices reach the market, small adjustments may be needed” -- have you tried approaching them? I see they also say “Sonos devices accept up to 48kHz/16bit audio” so perhaps they and Sonos would need to come to some kind of accommodation to increase the bit depth.