Tom PRO said about 2 years ago on Cropping Active Storage Uploads :
  Not sure if this is something you can deal with here (or perhaps an update episode for Rails 7), but this appears to be quite broken with Rails 7.0.1 - perhaps there are intervening changes with active storage?

Specifically, choosing an image from the file field, leads to a 500 with the log showing 'ActiveStorage::InvalidDirectUploadTokenError (ActiveStorage::InvalidDirectUploadTokenError):'
with the console showing:
TypeError: undefined is not an object (evaluating 'blob.signed_id')

(note that using the built-in 'direct_upload: true' on a file field does correctly work and upload, but of course, that doesn't produce nice cropping :)