Ah, that explains it. Thanks for the clarification. I will wait until the PPA and other releases catch up. In the meantime, I can always try that Debian package just to satisfy my curiosity.
Eagerly awaiting this new feature!
One thing I'm curious about is whether it will write yet another set of tags, specific to EBU R128; or will it overwrite the existing ReplayGain tags (created previously by MusicBee).