MP3Gain is an audio and music application which is used to adjust the volume levels of MP3 audio files. It can normalize audio levels across multiple tracks and albums, and can even adjust the overall volume level of an entire album. The app can also analyze the audio files and generate a ReplayGain value, which is an average loudness measurement of all tracks. The ReplayGain value can be used to ensure that all tracks within an album have the same average loudness. The app can also perform batch processing, which means that it can process multiple files at once. Additionally, the app can be used to convert audio files to different formats, such as MP3, WAV, and FLAC.
It is just an interface that supports several converters that must be installed separately, including an engine similar to MP3Gain, which may not even be possible to install as-is on Linux, so it is misleading to say that because SoundKonverter runs on Linux it is a Linux equivalent to MP3Gain. It is far from such a thing.
Works right out of the box, has the same interface design, plus it supports two other formats in addition to MP3
QMP3Gain
wxMP3gain
MP3Gain Express
Normalize
soundKonverter
easyMP3Gain
iVolume
AACGain
MP3 Normalizer
Sound Normalizer
QtGain
wxMP3Gain is an interface to MP3Gain, not a program that works similarly to MP3Gain.