Most streaming service Atmos comes down as 768 kb/s (Rings of power was the highest I've noted at 960 kb/s) for all 6 channels. A UHD Atmos or DTS-X track is typically more on the order of 4500 kb/s fof the 6 channels. The streams are definitely not a lossless track.
Like MP3 and other lossy codecs elsewhere, it's probably good enough for the average user who's happy to play it through their TV speakers or perhaps a modest soundbar. Even on a decent system, you probably won't notice too much out of order unless you're listening critically or have a lossless source to compare too. I personally go lossless whenever possible because I went to the cost and trouble to build a decent system - Why feed it compromised material instead of trying to get the most out of it?
If you do want a full lossless audio track, the only legal options that I'm aware of currently are to buy the UHD, or something like Kaleidescope. Both are pretty effective at punishing your wallet if you want full quality. Still, I will be quite sad when physical media goes and the compressed streams are the only common source left.
