On my iPad I was able to get it installed by checking the "not on this ipad" section in the app store "purchased" area. I checked on an ios 14 and 15 device and confirmed it works. I don't think I have a 16+ device to check on and I'm too concerned over losing the app and not being able to get it back to want to upgrade anything to that, but check it out - you may still be able to restore it if you downloaded it before