I can't tell the difference between the current Spotify best quality and a flac CD rip streamed from my NAS, so I'm not sure it's worth the bother. Are any of the other 'lossless' streaming services actually provably lossless - as in bit perfect identical to a CD rip? All the services add watermarks and other crap to the stream as I assume Spotify does too ...
I've never committed myself to the torture of a long critical listening test but the math and reports from ears that I trust tell me that depending on the source material, the lossless stream can be audibly detected from things like 320 kbps mp3. I hear various reports on what Spotify is actually delivering, very possibly something less. Without going into any big discussion on the subject let's just discuss the market. AFAIK, Of the major streamers Spotify is the last one to NOT offer a lossless tier at around the same price as Spotify's top "Premium" lossy stream. Market perception being what it is, it's long past time for them to poop or get off the pot. Tidal, Amazon, Qobuz, are way past Redbook using every click-bait word from MQA to 96-192-DSD-Atmos-3D- etc to attract the unwashed customer base.. Of all, the only one of real audible value is the Atmos files now being offered by a few and attractive to surround sound folks like myself.
I'm not immediately aware of any tests done on the streams from the lossless providers to determine how close their product is to a bit-perfect copy of a CD or better source. But I'll bet dollars to donuts that tests have been done and the results are out there, google would be your friend, but very possibly one or more of our members are aware of some such test results.