Because the imageManipulator documentation says it was designed for local, not network, images, I tried to download the image first using Filesystem.downloadAsync. Once again, it works fine in Android and not in iOS. The error given is "Unable to download file: Error Domain=NSURLErrorDomain Code=-1002 “unsupported URL” "
The problem is that the URL wasn’t readable on iOS for imageManipulator (and Expo’s FileSystem functions) because some of the sequences in the URL needed escaping. Wrapped it in JavaScript’s encodeURI() and the remote image was read just fine.