I guess I didnāt really understand what you have been looking for. You are only a couple of weeks into playing, so only are just learning a few cord shapes.
What do you need from an app? Just practice one minute changes with two chords and change them up a bit. Go to three if you want more of a challenge. You can use any metronome.
Write a few lists with different patterns using the chords you know. You can look up tables of common chord prs, but those will have many chords you havenāt approached yet.