Thank you!, I get “something went wrong” when I try to play this from the mobile app (of course), but it does play from the desktop app.

How did you find this by the way @Bumper  ? I tried some random tracks and none were lossless.

Everything I play usually has the lossless tag. Admittedly I’m not watching that closely but if I do look it’s always tagged lossless or will show lossless part way through the song. 
 

Not every player supports lossless FYI. I know playbase doesn’t there are others but that’s the only confirmed one from Sonos. 
 

Sometimes for me it’s very buggy with skips and lossless doesn’t show. This is with Ethernet wired amp and port. 

Most of the stuff I play ends up showing a lossless tag now.  Sometime the first song of a playlist or station won’t, but once it gets going, it shows up.  I’ve not noticed any real difference between wired or wireless speakers, but I do have pretty decent wifi in my house.