I started using the web browser, and both it and iTunes Music App sound the same to me for the ADM tracks.
I think it is working in Windows iTunes - at least I see "Apple Digital Masters" on albums, and audio sounds better than I remember iTunes sounding in general on all tracks - but the "Info" CTRL-I doesn't show "File" info with the bit rate reliably - some do and some don't have the "File" tab, and for "Preview" CTRL-I/Info is greyed out.
I'll eventually get around to trying "Paid" Apple Music (Lossless), I've still got Tidal MQA "Lossless" and Amazon Music HD "lossless" subscriptions I thoroughly enjoy listening to, so there is no rush.
Probably best to save that Free Trial for when Apple fills out the ADM albums and tracks inventory.