And because the App Store does not allow to download the last version of an app compatible with an outdated version of iOS, I [as a 6s-ipadPro1 owner] should in

And because the App Store does not allow to download the last version of an app compatible with an outdated version of iOS, I [as a 6s-ipadPro1 owner] should install now all the apps I need for the decades to come in their last iOS15-compatible version. Note: I did that for my ipad1. And guess what? Those apps still work like a charm.