i just converted a CD ("halber mensch" by einstürzende neubauten) into *.opus files with soundKonverter 2.0.5, then edited the metadata with easyTag 2.2.3, and finally rescanned my collection with amarok 2.8.0.
unfortunately, the files do not appear in my collection. when added to amarok's playlist via drag&drop, the files are played fine, but the metadata looks like a total mess, made up of parts from the file name and combined fields (e.g., the title field also contains the track number). it kinda fits the music. but it would be great if someone could try to replicate & solve this.
You need to have Amarok (>= 2.8) compiled against TagLib >= 1.9, see original bug.
*** This bug has been marked as a duplicate of bug 312905 ***
this *is* amarok 2.8.0 (with TagLib 1.9.1).
i recompiled amarok using the standard ubuntu package sources, and now it works! probably a packaging issue. sorry for the fuzz.