Even though EarTrain targets primarily those who want to develop perfect pitch, you can still use it to practice your relative pitch! With great success I might add! The only limit (as always) is your imagination.
This is how I tweaked it to practice relative pitch.
You can do the same with e.g., G# minor scale, pentatonic scale, frygian mode, etc. Once again, the only limit is your imagination! 😉
In the end, everything breaks down to individual notes.