Max2Play Home 2016 (en) › Forums › Max2Play as Squeezebox (Player / Server) › deezer plugin: plugins and their effect in general.. › Reply To: deezer plugin: plugins and their effect in general..
The plugins for LMS are third-party software and we can thus not guarantee any compatibility. The Deezer Plugin seems to require an active account on mysqueezebox and a Deezer Premium+ subscription. You might try it again with this course of action.
Regarding your second question, I am not sure which interface you mean when you say it shows up in the Squeezelite Player. TuneIn manages the radio functionalities of the LMS, this might be the reason it shows up.