There’s no longer anywhere in the very restricted x.x.x.x:1400/status diagnostic to discern the format/bandwidth.
Depending on the service, the controller may display the format (Deezer: “FLAC” vs “MP3”, Amazon: “UHD” vs “HD” vs “<no label>”) but I don’t believe it does with Tidal.
Your best bet would be to measure the actual stream bandwidth. Some routers offer this facility.
Just in case you weren’t aware: Sonos doesn’t support Tidal’s MQA, and almost certainly (and thankfully) never will.
TIDAL HiFi - Lossless FLAC 16bit/44.1kHz
TIDAL Premium - AAC 320kbps
https://support.sonos.com/s/article/3096?language=en_US
The OP is no doubt aware of that. The question is what bitrate Tidal is actually streaming at. When I evaluated it back in 2014/2015 I spotted a significant amount of AAC content on the ‘HiFi’ service. (There was even some at 96k, but hopefully that’s long gone.)
You can use my PC app (see profile) to see the bitrate that a stream is using from many music services (on S2).