Hello @Mesmo,
I want to try something different. Can you please try pasting the stream URL in Roon Radio on your Ubuntu Core? For example (http://icy1.abacast.com/kplu-newsjazzmp3-32)? Does this link work as expected?
If so you may be experiencing the same issue as this thread which QA is investigating now:
Please let me know if that link works and if it does you may be able to get the BBC stream working by posting the stream link instead of the tunein link (http://opml.radiotime.com/Tune.ashx?id=s24941&formats=mp3,aac)
Thanks,
Noris