Holla the forest fairy, there were probably unnoticed by me the day an update. And now does the app what it should.
Plays Mukke driven by any Spotify Client (tested with Win PC / Iphone / Android) easily from.
No connection problems etc.
Why not as Spotify?
Would not, however, still a native usable by remote client wish.
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Once there never was, since.
All versions up to date.
My solution to install the correct Spotify app via sideload. Then set up the part again with Remote Mouse for Fire TV.
Now funktionier Spotify connect