That’s the first approach I found to be recommended, but nope, didn’t work in this case for some reason. The app appeared as one I had indeed installed previous

That’s the first approach I found to be recommended, but nope, didn’t work in this case for some reason. The app appeared as one I had indeed installed previously (on my newer device) but still refused, saying a newer version of iOS was required. I wonder if it may have been because I had never downloaded the older version of GarageBand, only the latest one.