Is the tunein.groovy plugin currently working in Serviio v2 ?
Downloaded the (latest?) from the first post and installed.
Tried 3 options in Online Sources and playing in the MediaBrowser.
Used Web resource/audio ?
https://tunein.com/radio/Capital-London-958-s16534/ - did not appear in mediabrowser (note it works if you put the link into a browser)
https://tunein.com/radio/Christmas-UK-s298937/ - did not appear in mediabrowser
http://tunein.com/search/?query=capital - appeared in mediabrowser and displayed ten Capital stations - then played wrong station but OK now (after plugin change!).
Under DLNA nothing played.