Although Naim have support for Spotify Lossless already inside Gen 2 streamer units with up to date firmware, some customers have been finding that Spotify doesn’t offer it as available for their device, even though it should be.
If this is the case, the fix is to go into the Naim app, go to the device settings, Services and Accounts, and log out of Spotify.
Then go back to Spotify, reconnect, and it should now be working.
This fix seems to work for anyone with a Gen 2 Naim streamer who is seeing “This device is not compatible with Spotify Lossless”.
Note this is only for supported Naim streamer units - i.e. 2nd Generation.