Support for anything but the latest version available is very tough to maintain.
iOS 9.3 is the last version (3 major releases behind latest) for older iPads and iPhones.
iOS 9.3.x and Safari do not support CSS Grid. However, the error that is causing the white screen has nothing to do with this.
Since it is so old, it doesn't support the latest javascript arrow functions. The section of dashboard code that was using this has been fixed and back ported to support older browsers.
When this patch is deployed (most likely 2.0.9) older ipads and other browsers will support a limited subset of features for dashboard. Since grid isn't supported, it will just be a left to right, top to bottom list of tiles. It's enough for basic functionality, but position, order, layers, etc. will not be possible on older devices.
